Slide 1

Lecture Outlines
PowerPoint

Chapter 24
Earth Science 11e
Tarbuck/Lutgens
Modified for educational
purposes only
By S. Koziol 12-8-2010

© 2006 Pearson Prentice Hall

Earth Science, 11e
Beyond Our
Solar System
Chapter 24

24.1 Properties of stars
 Distance
•
•

Measuring a star's distance can be very
difficult
Stellar parallax
•
•
•

•
•

Used for measuring distance to a star
Apparent shift in a star's position due to the
orbital motion of Earth
Measured as an angle
Near stars have the largest parallax
Largest parallax is less than one second of arc

24. 1 Properties of stars
(continued)

 Distance
•
•

Distances to the stars are very large
Units of measurement
•
•

•

Kilometers or astronomical units are too
cumbersome to use
Light-year is used most often
• Distance that light travels in 1 year
• One light-year is 9.5 trillion km (5.8 trillion
miles)

Other methods for measuring distance are
also used

24. 1 Properties of stars
(continued)

 Stellar
•

Controlled by three factors
•

•
•

•

brightness

Size
Temperature
Distance

Magnitude
•

Measure of a star's brightness

24.1 Properties of stars
(continued)

 Stellar
•

brightness

Magnitude
•

Two types of measurement
• Apparent magnitude
• Brightness when a star is viewed from
Earth
• Decreases with distance
• Numbers are used to designate
magnitudes - dim stars have large
numbers and negative numbers are also
used

24.1 Properties of stars
(continued)

 Stellar
•

brightness

Magnitude
•

Two types of measurement
• Absolute magnitude
• "True" or intrinsic brightness of a star
• Brightness at a standard distance of
32.6 light-years
• Most stars' absolute magnitudes are
between -5 and +15

24.1 Properties of stars
(continued)

 Color
•

Hot star
•

•
•

•

and temperature

Temperature above 30,000 K
Emits short-wavelength light
Appears blue

Cool star
•
•
•

Temperature less than 3000 K
Emits longer-wavelength light
Appears red

24.1 Properties of stars
(continued)

 Color
•

and temperature

Between 5000 and 6000 K
•
•

Stars appear yellow
e.g., Sun

 Binary
•

stars and stellar mass

Binary stars
•

Two stars orbiting one another
• Stars are held together by mutual
gravitation
• Both orbit around a common center of mass

24.1 Properties of stars (continued)
 Binary
•

Binary stars
•

•
•

•

stars and stellar mass

Visual binaries are resolved telescopically
More than 50% of the stars in the universe are
binary stars
Used to determine stellar mass

Stellar mass
•

Determined using binary stars – the center of
mass is closest to the most massive star

Binary stars
orbit each
other around
their common
center of
mass
Figure 24.4

24.1 Properties of stars (continued)
 Binary
•

stars and stellar mass

Stellar mass
•

Mass of most stars is between one-tenth and
fifty times the mass of the Sun

24.1 Hertzsprung-Russell
diagram
 Shows
•
•

the relation between stellar

Brightness (absolute magnitude) and
Temperature

 Diagram

is made by plotting (graphing)
each star's
•
•

Luminosity (brightness) and
Temperature

24.1 Hertzsprung-Russell
diagram (continued)
 Parts
•

Main-sequence stars
•

•
•

•

of an H-R diagram

90% of all stars
Band through the center of the H-R diagram
Sun is in the main-sequence

Giants (or red giants)
•
•
•

Very luminous
Large
Upper-right on the H-R diagram

24.1 Hertzsprung-Russell
diagram (continued)
 Parts
•

Giants (or red giants)
•

•

•

of an H-R diagram

Very large giants are called supergiants
Only a few percent of all stars

White dwarfs
•
•

•
•
•

Fainter than main-sequence stars
Small (approximate the size of Earth)
Lower-central area on the H-R diagram
Not all are white in color
Perhaps 10% of all stars

Idealized HertzsprungRussell diagram

Figure 24.5

Quiz Break

24.2 Variable stars
 Stars

that fluctuate in brightness
 Types of variable stars
•

Pulsating variables
•
•

•

Fluctuate regularly in brightness
Expand and contract in size

Eruptive variables
•
•
•

Explosive event
Sudden brightening
Called a nova

24.2 Interstellar matter
 Between

the stars is "the vacuum of

space"
 Nebula
•
•

Cloud of dust and gases
Two major types of nebulae
•

Bright nebula
• Glows if it close to a very hot star
• Two types of bright nebulae
• Emission nebula
• Reflection nebula

The Orion Nebula is a wellknown emission nebula

Figure 24.8

A faint blue reflection nebula in
the Pleiades star cluster

Figure 24.9

24.2 Interstellar matter (continued)
 Nebula
•

Two major types of nebulae
•

Dark nebula
• Not close to any bright star
• Appear dark
• Contains the material that forms stars and
planets

24.2 Stellar evolution
 Stars

exist because of gravity
 Two opposing forces in a star are
•
•

Gravity – contracts
Thermal nuclear energy – expands

 Stages
•

Birth
•

•
•
•
•

In dark, cool, interstellar clouds
Gravity contracts the cloud
Temperature rises
Radiates long-wavelength (red) light
Becomes a protostar

24.2 Stellar evolution (continued)
 Stages
•

Protostar
•
•
•

•
•
•
•

Gravitational contraction of gaseous cloud
continues
Core reaches 10 million K
Hydrogen nuclei fuse
• Become helium nuclei
• Process is called hydrogen burning
Energy is released
Outward pressure increases
Outward pressure balanced by gravity pulling in
Star becomes a stable main-sequence star

24.2 Stellar evolution (continued)
 Stages
•

Main-sequence stage
•

Stars age at different rates
• Massive stars use fuel faster and exist for
only a few million years
• Small stars use fuel slowly and exist for
perhaps hundreds of billions of years

•

90% of a star's life is in the main-sequence

24.2 Stellar evolution (continued)
 Stages
•

Red giant stage
•
•

•
•
•

Hydrogen burning migrates outward
Star's outer envelope expands
• Surface cools
• Surface becomes red
Core is collapsing as helium is converted to
carbon
Eventually all nuclear fuel is used
Gravity squeezes the star

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Low-mass star
• 0.5 solar mass
• Red giant collapses
• Becomes a white dwarf

24.2 Evolutionary stages of
low mass stars

Figure 24.12 A

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Medium-mass star
• Between 0.5 and 3 solar masses
• Red giant collapses
• Planetary nebula forms
• Becomes a white dwarf

24.2 Evolutionary stages of
medium mass stars

Figure 24.12 B

H-R diagram showing
stellar evolution

Figure 24.11

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Massive star
• Over 3 solar masses
• Short life span
• Terminates in a brilliant explosion called
a supernova
• Interior condenses
• May produce a hot, dense object that is
either a neutron star or a black hole

24.2 Evolutionary stages of
massive stars

Figure 24.12 C

24.2 Stellar remnants
 White
•
•

Small (some no larger than Earth)
Dense
•
•
•

•
•

dwarf

Can be more massive than the Sun
Spoonful weighs several tons
Atoms take up less space
• Electrons displaced inward
• Called degenerate matter

Hot surface
Cools to become a black dwarf

24.2 Stellar remnants (continued)
 Neutron
•

Forms from a more massive star
•
•

•
•

star

Star has more gravity
Squeezes itself smaller

Remnant of a supernova
Gravitational force collapses atoms
•
•

Electrons combine with protons to produce
neutrons
Small size

24.2 Stellar remnants (continued)
 Neutron
•

Pea size sample
•
•

•
•

star

Weighs 100 million tons
Same density as an atomic nucleus

Strong magnetic field
First one discovered in early 1970s
•
•

Pulsar (pulsating radio source)
Found in the Crab nebula (remnant of an A.D.
1054 supernova)

Crab Nebula in the
constellation Taurus

Figure 24.14

24.2 Stellar remnants (continued)
 Black
•
•

•

More dense than a neutron star
Intense surface gravity lets no light escape
As matter is pulled into it
•
•

•

hole

Becomes very hot
Emits x-rays

Likely candidate is Cygnus X-1, a strong xray source

Quiz Break

24.3 Galaxies
 Milky
•

Way galaxy

Structure
•
•

•
•

Determined by using radio telescopes
Large spiral galaxy
• About 100,000 light-years wide
• Thickness at the galactic nucleus is about
10,000 light-years
Three spiral arms of stars
Sun is 30,000 light-years from the center

Face-on view of the
Milk Way Galaxy

Figure 24.18 A

Edge-on view of the
Milk Way Galaxy

Figure 24.18 B

24.3 Galaxies (continued)
 Milky
•

Rotation
•
•
•

•

Way galaxy

Around the galactic nucleus
Outermost stars move the slowest
Sun rotates around the galactic nucleus once
about every 200 million years

Halo surrounds the galactic disk
•
•
•

Spherical
Very tenuous gas
Numerous globular clusters

24.3 Galaxies (continued)
 Other
•
•

galaxies

Existence was first proposed in mid-1700s
by Immanuel Kant
Four basic types of galaxies
•

Spiral galaxy
• Arms extending from nucleus
• About 30% of all galaxies
• Large diameter of 20,000 to 125,000 light
years
• Contains both young and old stars
• e.g., Milky Way

Great Galaxy, a spiral galaxy, in
the constellation Andromeda

Figure 24.20

24.3 Galaxies (continued)
 Other
•

galaxies

Four basic types of galaxies
•

•

Barred spiral galaxy
• Stars arranged in the shape of a bar
• Generally quite large
• About 10% of all galaxies
Elliptical galaxy
• Ellipsoidal shape
• About 60% of all galaxies
• Most are smaller than spiral galaxies;
however, they are also the largest known
galaxies

A barred spiral galaxy

Figure 24.22

24.3 Galaxies (continued)
 Other
•

galaxies

Four basic types of galaxies
•

Irregular galaxy
• Lacks symmetry
• About 10% of all galaxies
• Contains mostly young stars
• e.g., Magellanic Clouds

24.3 Galaxies (continued)
 Galactic
•
•
•

Group of galaxies
Some contain thousands of galaxies
Local Group
•
•

•

cluster

Our own group of galaxies
Contains at least 28 galaxies

Supercluster
•
•

Huge swarm of galaxies
May be the largest entity in the universe

Quiz Break

24.4 Red shifts
 Doppler
•

effect

Change in the wavelength of light emitted
by an object due to its motion
•

•

Movement away stretches the wavelength
• Longer wavelength
• Light appears redder
Movement toward “squeezes” the wavelength
• Shorter wavelength
• Light shifted toward the blue

24.4 Red shifts (continued)
 Doppler
•

effect

Amount of the Doppler shift indicates the
rate of movement
•
•

Large Doppler shift indicates a high velocity
Small Doppler shift indicates a lower velocity

 Expanding
•

universe

Most galaxies exhibit a red Doppler shift
•

Moving away

Raisin bread analogy of an
expanding universe

Figure 24.24

24.4 Red shifts (continued)
 Expanding
•

universe

Most galaxies exhibit a red Doppler shift
•

•
•
•

Far galaxies
• Exhibit the greatest shift
• Greater velocity
Discovered in 1929 by Edwin Hubble
Hubble's Law – the recessional speed of
galaxies is proportional to their distance
Accounts for red shifts

24.4 Big Bang theory
 Accounts

for galaxies moving away

from us
 Universe was once confined to a "ball"
that was
•
•

•

Supermassive
Dense
Hot

24.4 Big Bang theory (continued)
 Big

Bang marks the inception of the
universe
•
•

Occurred about 15 billion years ago
All matter and space was created

 Matter

is moving outward
 Fate of the universe
•

Two possibilities
•
•

Universe will last forever
Outward expansion sill stop and gravitational;
contraction will follow

24.4 Big Bang theory (continued)
 Fate
•

of the universe

Final fate depends on the average density
of the universe
•
•

If the density is more than the critical density,
then the universe would contract
Current estimates point to less then the critical
density and predict an ever-expanding, or
open, universe

Chapter 24Test Guidance
You will be responsible on the test for answering 3 of the following 6
questions.
1.

2.

3.
4.
5.
6.

What causes the difference between a star’s apparent
magnitude and it absolute magnitude.
List and explain the three factors that control the apparent
brightness of a star as seen from Earth.
Describe how binary stars are used to determine stellar mass.
List and describe the four basic types of galaxies.
What is Hubble’s Law, please explain in detail.
Briefly describe the Big Bang Theory (not the TV show).

End of Chapter 24


Slide 2

Lecture Outlines
PowerPoint

Chapter 24
Earth Science 11e
Tarbuck/Lutgens
Modified for educational
purposes only
By S. Koziol 12-8-2010

© 2006 Pearson Prentice Hall

Earth Science, 11e
Beyond Our
Solar System
Chapter 24

24.1 Properties of stars
 Distance
•
•

Measuring a star's distance can be very
difficult
Stellar parallax
•
•
•

•
•

Used for measuring distance to a star
Apparent shift in a star's position due to the
orbital motion of Earth
Measured as an angle
Near stars have the largest parallax
Largest parallax is less than one second of arc

24. 1 Properties of stars
(continued)

 Distance
•
•

Distances to the stars are very large
Units of measurement
•
•

•

Kilometers or astronomical units are too
cumbersome to use
Light-year is used most often
• Distance that light travels in 1 year
• One light-year is 9.5 trillion km (5.8 trillion
miles)

Other methods for measuring distance are
also used

24. 1 Properties of stars
(continued)

 Stellar
•

Controlled by three factors
•

•
•

•

brightness

Size
Temperature
Distance

Magnitude
•

Measure of a star's brightness

24.1 Properties of stars
(continued)

 Stellar
•

brightness

Magnitude
•

Two types of measurement
• Apparent magnitude
• Brightness when a star is viewed from
Earth
• Decreases with distance
• Numbers are used to designate
magnitudes - dim stars have large
numbers and negative numbers are also
used

24.1 Properties of stars
(continued)

 Stellar
•

brightness

Magnitude
•

Two types of measurement
• Absolute magnitude
• "True" or intrinsic brightness of a star
• Brightness at a standard distance of
32.6 light-years
• Most stars' absolute magnitudes are
between -5 and +15

24.1 Properties of stars
(continued)

 Color
•

Hot star
•

•
•

•

and temperature

Temperature above 30,000 K
Emits short-wavelength light
Appears blue

Cool star
•
•
•

Temperature less than 3000 K
Emits longer-wavelength light
Appears red

24.1 Properties of stars
(continued)

 Color
•

and temperature

Between 5000 and 6000 K
•
•

Stars appear yellow
e.g., Sun

 Binary
•

stars and stellar mass

Binary stars
•

Two stars orbiting one another
• Stars are held together by mutual
gravitation
• Both orbit around a common center of mass

24.1 Properties of stars (continued)
 Binary
•

Binary stars
•

•
•

•

stars and stellar mass

Visual binaries are resolved telescopically
More than 50% of the stars in the universe are
binary stars
Used to determine stellar mass

Stellar mass
•

Determined using binary stars – the center of
mass is closest to the most massive star

Binary stars
orbit each
other around
their common
center of
mass
Figure 24.4

24.1 Properties of stars (continued)
 Binary
•

stars and stellar mass

Stellar mass
•

Mass of most stars is between one-tenth and
fifty times the mass of the Sun

24.1 Hertzsprung-Russell
diagram
 Shows
•
•

the relation between stellar

Brightness (absolute magnitude) and
Temperature

 Diagram

is made by plotting (graphing)
each star's
•
•

Luminosity (brightness) and
Temperature

24.1 Hertzsprung-Russell
diagram (continued)
 Parts
•

Main-sequence stars
•

•
•

•

of an H-R diagram

90% of all stars
Band through the center of the H-R diagram
Sun is in the main-sequence

Giants (or red giants)
•
•
•

Very luminous
Large
Upper-right on the H-R diagram

24.1 Hertzsprung-Russell
diagram (continued)
 Parts
•

Giants (or red giants)
•

•

•

of an H-R diagram

Very large giants are called supergiants
Only a few percent of all stars

White dwarfs
•
•

•
•
•

Fainter than main-sequence stars
Small (approximate the size of Earth)
Lower-central area on the H-R diagram
Not all are white in color
Perhaps 10% of all stars

Idealized HertzsprungRussell diagram

Figure 24.5

Quiz Break

24.2 Variable stars
 Stars

that fluctuate in brightness
 Types of variable stars
•

Pulsating variables
•
•

•

Fluctuate regularly in brightness
Expand and contract in size

Eruptive variables
•
•
•

Explosive event
Sudden brightening
Called a nova

24.2 Interstellar matter
 Between

the stars is "the vacuum of

space"
 Nebula
•
•

Cloud of dust and gases
Two major types of nebulae
•

Bright nebula
• Glows if it close to a very hot star
• Two types of bright nebulae
• Emission nebula
• Reflection nebula

The Orion Nebula is a wellknown emission nebula

Figure 24.8

A faint blue reflection nebula in
the Pleiades star cluster

Figure 24.9

24.2 Interstellar matter (continued)
 Nebula
•

Two major types of nebulae
•

Dark nebula
• Not close to any bright star
• Appear dark
• Contains the material that forms stars and
planets

24.2 Stellar evolution
 Stars

exist because of gravity
 Two opposing forces in a star are
•
•

Gravity – contracts
Thermal nuclear energy – expands

 Stages
•

Birth
•

•
•
•
•

In dark, cool, interstellar clouds
Gravity contracts the cloud
Temperature rises
Radiates long-wavelength (red) light
Becomes a protostar

24.2 Stellar evolution (continued)
 Stages
•

Protostar
•
•
•

•
•
•
•

Gravitational contraction of gaseous cloud
continues
Core reaches 10 million K
Hydrogen nuclei fuse
• Become helium nuclei
• Process is called hydrogen burning
Energy is released
Outward pressure increases
Outward pressure balanced by gravity pulling in
Star becomes a stable main-sequence star

24.2 Stellar evolution (continued)
 Stages
•

Main-sequence stage
•

Stars age at different rates
• Massive stars use fuel faster and exist for
only a few million years
• Small stars use fuel slowly and exist for
perhaps hundreds of billions of years

•

90% of a star's life is in the main-sequence

24.2 Stellar evolution (continued)
 Stages
•

Red giant stage
•
•

•
•
•

Hydrogen burning migrates outward
Star's outer envelope expands
• Surface cools
• Surface becomes red
Core is collapsing as helium is converted to
carbon
Eventually all nuclear fuel is used
Gravity squeezes the star

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Low-mass star
• 0.5 solar mass
• Red giant collapses
• Becomes a white dwarf

24.2 Evolutionary stages of
low mass stars

Figure 24.12 A

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Medium-mass star
• Between 0.5 and 3 solar masses
• Red giant collapses
• Planetary nebula forms
• Becomes a white dwarf

24.2 Evolutionary stages of
medium mass stars

Figure 24.12 B

H-R diagram showing
stellar evolution

Figure 24.11

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Massive star
• Over 3 solar masses
• Short life span
• Terminates in a brilliant explosion called
a supernova
• Interior condenses
• May produce a hot, dense object that is
either a neutron star or a black hole

24.2 Evolutionary stages of
massive stars

Figure 24.12 C

24.2 Stellar remnants
 White
•
•

Small (some no larger than Earth)
Dense
•
•
•

•
•

dwarf

Can be more massive than the Sun
Spoonful weighs several tons
Atoms take up less space
• Electrons displaced inward
• Called degenerate matter

Hot surface
Cools to become a black dwarf

24.2 Stellar remnants (continued)
 Neutron
•

Forms from a more massive star
•
•

•
•

star

Star has more gravity
Squeezes itself smaller

Remnant of a supernova
Gravitational force collapses atoms
•
•

Electrons combine with protons to produce
neutrons
Small size

24.2 Stellar remnants (continued)
 Neutron
•

Pea size sample
•
•

•
•

star

Weighs 100 million tons
Same density as an atomic nucleus

Strong magnetic field
First one discovered in early 1970s
•
•

Pulsar (pulsating radio source)
Found in the Crab nebula (remnant of an A.D.
1054 supernova)

Crab Nebula in the
constellation Taurus

Figure 24.14

24.2 Stellar remnants (continued)
 Black
•
•

•

More dense than a neutron star
Intense surface gravity lets no light escape
As matter is pulled into it
•
•

•

hole

Becomes very hot
Emits x-rays

Likely candidate is Cygnus X-1, a strong xray source

Quiz Break

24.3 Galaxies
 Milky
•

Way galaxy

Structure
•
•

•
•

Determined by using radio telescopes
Large spiral galaxy
• About 100,000 light-years wide
• Thickness at the galactic nucleus is about
10,000 light-years
Three spiral arms of stars
Sun is 30,000 light-years from the center

Face-on view of the
Milk Way Galaxy

Figure 24.18 A

Edge-on view of the
Milk Way Galaxy

Figure 24.18 B

24.3 Galaxies (continued)
 Milky
•

Rotation
•
•
•

•

Way galaxy

Around the galactic nucleus
Outermost stars move the slowest
Sun rotates around the galactic nucleus once
about every 200 million years

Halo surrounds the galactic disk
•
•
•

Spherical
Very tenuous gas
Numerous globular clusters

24.3 Galaxies (continued)
 Other
•
•

galaxies

Existence was first proposed in mid-1700s
by Immanuel Kant
Four basic types of galaxies
•

Spiral galaxy
• Arms extending from nucleus
• About 30% of all galaxies
• Large diameter of 20,000 to 125,000 light
years
• Contains both young and old stars
• e.g., Milky Way

Great Galaxy, a spiral galaxy, in
the constellation Andromeda

Figure 24.20

24.3 Galaxies (continued)
 Other
•

galaxies

Four basic types of galaxies
•

•

Barred spiral galaxy
• Stars arranged in the shape of a bar
• Generally quite large
• About 10% of all galaxies
Elliptical galaxy
• Ellipsoidal shape
• About 60% of all galaxies
• Most are smaller than spiral galaxies;
however, they are also the largest known
galaxies

A barred spiral galaxy

Figure 24.22

24.3 Galaxies (continued)
 Other
•

galaxies

Four basic types of galaxies
•

Irregular galaxy
• Lacks symmetry
• About 10% of all galaxies
• Contains mostly young stars
• e.g., Magellanic Clouds

24.3 Galaxies (continued)
 Galactic
•
•
•

Group of galaxies
Some contain thousands of galaxies
Local Group
•
•

•

cluster

Our own group of galaxies
Contains at least 28 galaxies

Supercluster
•
•

Huge swarm of galaxies
May be the largest entity in the universe

Quiz Break

24.4 Red shifts
 Doppler
•

effect

Change in the wavelength of light emitted
by an object due to its motion
•

•

Movement away stretches the wavelength
• Longer wavelength
• Light appears redder
Movement toward “squeezes” the wavelength
• Shorter wavelength
• Light shifted toward the blue

24.4 Red shifts (continued)
 Doppler
•

effect

Amount of the Doppler shift indicates the
rate of movement
•
•

Large Doppler shift indicates a high velocity
Small Doppler shift indicates a lower velocity

 Expanding
•

universe

Most galaxies exhibit a red Doppler shift
•

Moving away

Raisin bread analogy of an
expanding universe

Figure 24.24

24.4 Red shifts (continued)
 Expanding
•

universe

Most galaxies exhibit a red Doppler shift
•

•
•
•

Far galaxies
• Exhibit the greatest shift
• Greater velocity
Discovered in 1929 by Edwin Hubble
Hubble's Law – the recessional speed of
galaxies is proportional to their distance
Accounts for red shifts

24.4 Big Bang theory
 Accounts

for galaxies moving away

from us
 Universe was once confined to a "ball"
that was
•
•

•

Supermassive
Dense
Hot

24.4 Big Bang theory (continued)
 Big

Bang marks the inception of the
universe
•
•

Occurred about 15 billion years ago
All matter and space was created

 Matter

is moving outward
 Fate of the universe
•

Two possibilities
•
•

Universe will last forever
Outward expansion sill stop and gravitational;
contraction will follow

24.4 Big Bang theory (continued)
 Fate
•

of the universe

Final fate depends on the average density
of the universe
•
•

If the density is more than the critical density,
then the universe would contract
Current estimates point to less then the critical
density and predict an ever-expanding, or
open, universe

Chapter 24Test Guidance
You will be responsible on the test for answering 3 of the following 6
questions.
1.

2.

3.
4.
5.
6.

What causes the difference between a star’s apparent
magnitude and it absolute magnitude.
List and explain the three factors that control the apparent
brightness of a star as seen from Earth.
Describe how binary stars are used to determine stellar mass.
List and describe the four basic types of galaxies.
What is Hubble’s Law, please explain in detail.
Briefly describe the Big Bang Theory (not the TV show).

End of Chapter 24


Slide 3

Lecture Outlines
PowerPoint

Chapter 24
Earth Science 11e
Tarbuck/Lutgens
Modified for educational
purposes only
By S. Koziol 12-8-2010

© 2006 Pearson Prentice Hall

Earth Science, 11e
Beyond Our
Solar System
Chapter 24

24.1 Properties of stars
 Distance
•
•

Measuring a star's distance can be very
difficult
Stellar parallax
•
•
•

•
•

Used for measuring distance to a star
Apparent shift in a star's position due to the
orbital motion of Earth
Measured as an angle
Near stars have the largest parallax
Largest parallax is less than one second of arc

24. 1 Properties of stars
(continued)

 Distance
•
•

Distances to the stars are very large
Units of measurement
•
•

•

Kilometers or astronomical units are too
cumbersome to use
Light-year is used most often
• Distance that light travels in 1 year
• One light-year is 9.5 trillion km (5.8 trillion
miles)

Other methods for measuring distance are
also used

24. 1 Properties of stars
(continued)

 Stellar
•

Controlled by three factors
•

•
•

•

brightness

Size
Temperature
Distance

Magnitude
•

Measure of a star's brightness

24.1 Properties of stars
(continued)

 Stellar
•

brightness

Magnitude
•

Two types of measurement
• Apparent magnitude
• Brightness when a star is viewed from
Earth
• Decreases with distance
• Numbers are used to designate
magnitudes - dim stars have large
numbers and negative numbers are also
used

24.1 Properties of stars
(continued)

 Stellar
•

brightness

Magnitude
•

Two types of measurement
• Absolute magnitude
• "True" or intrinsic brightness of a star
• Brightness at a standard distance of
32.6 light-years
• Most stars' absolute magnitudes are
between -5 and +15

24.1 Properties of stars
(continued)

 Color
•

Hot star
•

•
•

•

and temperature

Temperature above 30,000 K
Emits short-wavelength light
Appears blue

Cool star
•
•
•

Temperature less than 3000 K
Emits longer-wavelength light
Appears red

24.1 Properties of stars
(continued)

 Color
•

and temperature

Between 5000 and 6000 K
•
•

Stars appear yellow
e.g., Sun

 Binary
•

stars and stellar mass

Binary stars
•

Two stars orbiting one another
• Stars are held together by mutual
gravitation
• Both orbit around a common center of mass

24.1 Properties of stars (continued)
 Binary
•

Binary stars
•

•
•

•

stars and stellar mass

Visual binaries are resolved telescopically
More than 50% of the stars in the universe are
binary stars
Used to determine stellar mass

Stellar mass
•

Determined using binary stars – the center of
mass is closest to the most massive star

Binary stars
orbit each
other around
their common
center of
mass
Figure 24.4

24.1 Properties of stars (continued)
 Binary
•

stars and stellar mass

Stellar mass
•

Mass of most stars is between one-tenth and
fifty times the mass of the Sun

24.1 Hertzsprung-Russell
diagram
 Shows
•
•

the relation between stellar

Brightness (absolute magnitude) and
Temperature

 Diagram

is made by plotting (graphing)
each star's
•
•

Luminosity (brightness) and
Temperature

24.1 Hertzsprung-Russell
diagram (continued)
 Parts
•

Main-sequence stars
•

•
•

•

of an H-R diagram

90% of all stars
Band through the center of the H-R diagram
Sun is in the main-sequence

Giants (or red giants)
•
•
•

Very luminous
Large
Upper-right on the H-R diagram

24.1 Hertzsprung-Russell
diagram (continued)
 Parts
•

Giants (or red giants)
•

•

•

of an H-R diagram

Very large giants are called supergiants
Only a few percent of all stars

White dwarfs
•
•

•
•
•

Fainter than main-sequence stars
Small (approximate the size of Earth)
Lower-central area on the H-R diagram
Not all are white in color
Perhaps 10% of all stars

Idealized HertzsprungRussell diagram

Figure 24.5

Quiz Break

24.2 Variable stars
 Stars

that fluctuate in brightness
 Types of variable stars
•

Pulsating variables
•
•

•

Fluctuate regularly in brightness
Expand and contract in size

Eruptive variables
•
•
•

Explosive event
Sudden brightening
Called a nova

24.2 Interstellar matter
 Between

the stars is "the vacuum of

space"
 Nebula
•
•

Cloud of dust and gases
Two major types of nebulae
•

Bright nebula
• Glows if it close to a very hot star
• Two types of bright nebulae
• Emission nebula
• Reflection nebula

The Orion Nebula is a wellknown emission nebula

Figure 24.8

A faint blue reflection nebula in
the Pleiades star cluster

Figure 24.9

24.2 Interstellar matter (continued)
 Nebula
•

Two major types of nebulae
•

Dark nebula
• Not close to any bright star
• Appear dark
• Contains the material that forms stars and
planets

24.2 Stellar evolution
 Stars

exist because of gravity
 Two opposing forces in a star are
•
•

Gravity – contracts
Thermal nuclear energy – expands

 Stages
•

Birth
•

•
•
•
•

In dark, cool, interstellar clouds
Gravity contracts the cloud
Temperature rises
Radiates long-wavelength (red) light
Becomes a protostar

24.2 Stellar evolution (continued)
 Stages
•

Protostar
•
•
•

•
•
•
•

Gravitational contraction of gaseous cloud
continues
Core reaches 10 million K
Hydrogen nuclei fuse
• Become helium nuclei
• Process is called hydrogen burning
Energy is released
Outward pressure increases
Outward pressure balanced by gravity pulling in
Star becomes a stable main-sequence star

24.2 Stellar evolution (continued)
 Stages
•

Main-sequence stage
•

Stars age at different rates
• Massive stars use fuel faster and exist for
only a few million years
• Small stars use fuel slowly and exist for
perhaps hundreds of billions of years

•

90% of a star's life is in the main-sequence

24.2 Stellar evolution (continued)
 Stages
•

Red giant stage
•
•

•
•
•

Hydrogen burning migrates outward
Star's outer envelope expands
• Surface cools
• Surface becomes red
Core is collapsing as helium is converted to
carbon
Eventually all nuclear fuel is used
Gravity squeezes the star

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Low-mass star
• 0.5 solar mass
• Red giant collapses
• Becomes a white dwarf

24.2 Evolutionary stages of
low mass stars

Figure 24.12 A

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Medium-mass star
• Between 0.5 and 3 solar masses
• Red giant collapses
• Planetary nebula forms
• Becomes a white dwarf

24.2 Evolutionary stages of
medium mass stars

Figure 24.12 B

H-R diagram showing
stellar evolution

Figure 24.11

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Massive star
• Over 3 solar masses
• Short life span
• Terminates in a brilliant explosion called
a supernova
• Interior condenses
• May produce a hot, dense object that is
either a neutron star or a black hole

24.2 Evolutionary stages of
massive stars

Figure 24.12 C

24.2 Stellar remnants
 White
•
•

Small (some no larger than Earth)
Dense
•
•
•

•
•

dwarf

Can be more massive than the Sun
Spoonful weighs several tons
Atoms take up less space
• Electrons displaced inward
• Called degenerate matter

Hot surface
Cools to become a black dwarf

24.2 Stellar remnants (continued)
 Neutron
•

Forms from a more massive star
•
•

•
•

star

Star has more gravity
Squeezes itself smaller

Remnant of a supernova
Gravitational force collapses atoms
•
•

Electrons combine with protons to produce
neutrons
Small size

24.2 Stellar remnants (continued)
 Neutron
•

Pea size sample
•
•

•
•

star

Weighs 100 million tons
Same density as an atomic nucleus

Strong magnetic field
First one discovered in early 1970s
•
•

Pulsar (pulsating radio source)
Found in the Crab nebula (remnant of an A.D.
1054 supernova)

Crab Nebula in the
constellation Taurus

Figure 24.14

24.2 Stellar remnants (continued)
 Black
•
•

•

More dense than a neutron star
Intense surface gravity lets no light escape
As matter is pulled into it
•
•

•

hole

Becomes very hot
Emits x-rays

Likely candidate is Cygnus X-1, a strong xray source

Quiz Break

24.3 Galaxies
 Milky
•

Way galaxy

Structure
•
•

•
•

Determined by using radio telescopes
Large spiral galaxy
• About 100,000 light-years wide
• Thickness at the galactic nucleus is about
10,000 light-years
Three spiral arms of stars
Sun is 30,000 light-years from the center

Face-on view of the
Milk Way Galaxy

Figure 24.18 A

Edge-on view of the
Milk Way Galaxy

Figure 24.18 B

24.3 Galaxies (continued)
 Milky
•

Rotation
•
•
•

•

Way galaxy

Around the galactic nucleus
Outermost stars move the slowest
Sun rotates around the galactic nucleus once
about every 200 million years

Halo surrounds the galactic disk
•
•
•

Spherical
Very tenuous gas
Numerous globular clusters

24.3 Galaxies (continued)
 Other
•
•

galaxies

Existence was first proposed in mid-1700s
by Immanuel Kant
Four basic types of galaxies
•

Spiral galaxy
• Arms extending from nucleus
• About 30% of all galaxies
• Large diameter of 20,000 to 125,000 light
years
• Contains both young and old stars
• e.g., Milky Way

Great Galaxy, a spiral galaxy, in
the constellation Andromeda

Figure 24.20

24.3 Galaxies (continued)
 Other
•

galaxies

Four basic types of galaxies
•

•

Barred spiral galaxy
• Stars arranged in the shape of a bar
• Generally quite large
• About 10% of all galaxies
Elliptical galaxy
• Ellipsoidal shape
• About 60% of all galaxies
• Most are smaller than spiral galaxies;
however, they are also the largest known
galaxies

A barred spiral galaxy

Figure 24.22

24.3 Galaxies (continued)
 Other
•

galaxies

Four basic types of galaxies
•

Irregular galaxy
• Lacks symmetry
• About 10% of all galaxies
• Contains mostly young stars
• e.g., Magellanic Clouds

24.3 Galaxies (continued)
 Galactic
•
•
•

Group of galaxies
Some contain thousands of galaxies
Local Group
•
•

•

cluster

Our own group of galaxies
Contains at least 28 galaxies

Supercluster
•
•

Huge swarm of galaxies
May be the largest entity in the universe

Quiz Break

24.4 Red shifts
 Doppler
•

effect

Change in the wavelength of light emitted
by an object due to its motion
•

•

Movement away stretches the wavelength
• Longer wavelength
• Light appears redder
Movement toward “squeezes” the wavelength
• Shorter wavelength
• Light shifted toward the blue

24.4 Red shifts (continued)
 Doppler
•

effect

Amount of the Doppler shift indicates the
rate of movement
•
•

Large Doppler shift indicates a high velocity
Small Doppler shift indicates a lower velocity

 Expanding
•

universe

Most galaxies exhibit a red Doppler shift
•

Moving away

Raisin bread analogy of an
expanding universe

Figure 24.24

24.4 Red shifts (continued)
 Expanding
•

universe

Most galaxies exhibit a red Doppler shift
•

•
•
•

Far galaxies
• Exhibit the greatest shift
• Greater velocity
Discovered in 1929 by Edwin Hubble
Hubble's Law – the recessional speed of
galaxies is proportional to their distance
Accounts for red shifts

24.4 Big Bang theory
 Accounts

for galaxies moving away

from us
 Universe was once confined to a "ball"
that was
•
•

•

Supermassive
Dense
Hot

24.4 Big Bang theory (continued)
 Big

Bang marks the inception of the
universe
•
•

Occurred about 15 billion years ago
All matter and space was created

 Matter

is moving outward
 Fate of the universe
•

Two possibilities
•
•

Universe will last forever
Outward expansion sill stop and gravitational;
contraction will follow

24.4 Big Bang theory (continued)
 Fate
•

of the universe

Final fate depends on the average density
of the universe
•
•

If the density is more than the critical density,
then the universe would contract
Current estimates point to less then the critical
density and predict an ever-expanding, or
open, universe

Chapter 24Test Guidance
You will be responsible on the test for answering 3 of the following 6
questions.
1.

2.

3.
4.
5.
6.

What causes the difference between a star’s apparent
magnitude and it absolute magnitude.
List and explain the three factors that control the apparent
brightness of a star as seen from Earth.
Describe how binary stars are used to determine stellar mass.
List and describe the four basic types of galaxies.
What is Hubble’s Law, please explain in detail.
Briefly describe the Big Bang Theory (not the TV show).

End of Chapter 24


Slide 4

Lecture Outlines
PowerPoint

Chapter 24
Earth Science 11e
Tarbuck/Lutgens
Modified for educational
purposes only
By S. Koziol 12-8-2010

© 2006 Pearson Prentice Hall

Earth Science, 11e
Beyond Our
Solar System
Chapter 24

24.1 Properties of stars
 Distance
•
•

Measuring a star's distance can be very
difficult
Stellar parallax
•
•
•

•
•

Used for measuring distance to a star
Apparent shift in a star's position due to the
orbital motion of Earth
Measured as an angle
Near stars have the largest parallax
Largest parallax is less than one second of arc

24. 1 Properties of stars
(continued)

 Distance
•
•

Distances to the stars are very large
Units of measurement
•
•

•

Kilometers or astronomical units are too
cumbersome to use
Light-year is used most often
• Distance that light travels in 1 year
• One light-year is 9.5 trillion km (5.8 trillion
miles)

Other methods for measuring distance are
also used

24. 1 Properties of stars
(continued)

 Stellar
•

Controlled by three factors
•

•
•

•

brightness

Size
Temperature
Distance

Magnitude
•

Measure of a star's brightness

24.1 Properties of stars
(continued)

 Stellar
•

brightness

Magnitude
•

Two types of measurement
• Apparent magnitude
• Brightness when a star is viewed from
Earth
• Decreases with distance
• Numbers are used to designate
magnitudes - dim stars have large
numbers and negative numbers are also
used

24.1 Properties of stars
(continued)

 Stellar
•

brightness

Magnitude
•

Two types of measurement
• Absolute magnitude
• "True" or intrinsic brightness of a star
• Brightness at a standard distance of
32.6 light-years
• Most stars' absolute magnitudes are
between -5 and +15

24.1 Properties of stars
(continued)

 Color
•

Hot star
•

•
•

•

and temperature

Temperature above 30,000 K
Emits short-wavelength light
Appears blue

Cool star
•
•
•

Temperature less than 3000 K
Emits longer-wavelength light
Appears red

24.1 Properties of stars
(continued)

 Color
•

and temperature

Between 5000 and 6000 K
•
•

Stars appear yellow
e.g., Sun

 Binary
•

stars and stellar mass

Binary stars
•

Two stars orbiting one another
• Stars are held together by mutual
gravitation
• Both orbit around a common center of mass

24.1 Properties of stars (continued)
 Binary
•

Binary stars
•

•
•

•

stars and stellar mass

Visual binaries are resolved telescopically
More than 50% of the stars in the universe are
binary stars
Used to determine stellar mass

Stellar mass
•

Determined using binary stars – the center of
mass is closest to the most massive star

Binary stars
orbit each
other around
their common
center of
mass
Figure 24.4

24.1 Properties of stars (continued)
 Binary
•

stars and stellar mass

Stellar mass
•

Mass of most stars is between one-tenth and
fifty times the mass of the Sun

24.1 Hertzsprung-Russell
diagram
 Shows
•
•

the relation between stellar

Brightness (absolute magnitude) and
Temperature

 Diagram

is made by plotting (graphing)
each star's
•
•

Luminosity (brightness) and
Temperature

24.1 Hertzsprung-Russell
diagram (continued)
 Parts
•

Main-sequence stars
•

•
•

•

of an H-R diagram

90% of all stars
Band through the center of the H-R diagram
Sun is in the main-sequence

Giants (or red giants)
•
•
•

Very luminous
Large
Upper-right on the H-R diagram

24.1 Hertzsprung-Russell
diagram (continued)
 Parts
•

Giants (or red giants)
•

•

•

of an H-R diagram

Very large giants are called supergiants
Only a few percent of all stars

White dwarfs
•
•

•
•
•

Fainter than main-sequence stars
Small (approximate the size of Earth)
Lower-central area on the H-R diagram
Not all are white in color
Perhaps 10% of all stars

Idealized HertzsprungRussell diagram

Figure 24.5

Quiz Break

24.2 Variable stars
 Stars

that fluctuate in brightness
 Types of variable stars
•

Pulsating variables
•
•

•

Fluctuate regularly in brightness
Expand and contract in size

Eruptive variables
•
•
•

Explosive event
Sudden brightening
Called a nova

24.2 Interstellar matter
 Between

the stars is "the vacuum of

space"
 Nebula
•
•

Cloud of dust and gases
Two major types of nebulae
•

Bright nebula
• Glows if it close to a very hot star
• Two types of bright nebulae
• Emission nebula
• Reflection nebula

The Orion Nebula is a wellknown emission nebula

Figure 24.8

A faint blue reflection nebula in
the Pleiades star cluster

Figure 24.9

24.2 Interstellar matter (continued)
 Nebula
•

Two major types of nebulae
•

Dark nebula
• Not close to any bright star
• Appear dark
• Contains the material that forms stars and
planets

24.2 Stellar evolution
 Stars

exist because of gravity
 Two opposing forces in a star are
•
•

Gravity – contracts
Thermal nuclear energy – expands

 Stages
•

Birth
•

•
•
•
•

In dark, cool, interstellar clouds
Gravity contracts the cloud
Temperature rises
Radiates long-wavelength (red) light
Becomes a protostar

24.2 Stellar evolution (continued)
 Stages
•

Protostar
•
•
•

•
•
•
•

Gravitational contraction of gaseous cloud
continues
Core reaches 10 million K
Hydrogen nuclei fuse
• Become helium nuclei
• Process is called hydrogen burning
Energy is released
Outward pressure increases
Outward pressure balanced by gravity pulling in
Star becomes a stable main-sequence star

24.2 Stellar evolution (continued)
 Stages
•

Main-sequence stage
•

Stars age at different rates
• Massive stars use fuel faster and exist for
only a few million years
• Small stars use fuel slowly and exist for
perhaps hundreds of billions of years

•

90% of a star's life is in the main-sequence

24.2 Stellar evolution (continued)
 Stages
•

Red giant stage
•
•

•
•
•

Hydrogen burning migrates outward
Star's outer envelope expands
• Surface cools
• Surface becomes red
Core is collapsing as helium is converted to
carbon
Eventually all nuclear fuel is used
Gravity squeezes the star

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Low-mass star
• 0.5 solar mass
• Red giant collapses
• Becomes a white dwarf

24.2 Evolutionary stages of
low mass stars

Figure 24.12 A

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Medium-mass star
• Between 0.5 and 3 solar masses
• Red giant collapses
• Planetary nebula forms
• Becomes a white dwarf

24.2 Evolutionary stages of
medium mass stars

Figure 24.12 B

H-R diagram showing
stellar evolution

Figure 24.11

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Massive star
• Over 3 solar masses
• Short life span
• Terminates in a brilliant explosion called
a supernova
• Interior condenses
• May produce a hot, dense object that is
either a neutron star or a black hole

24.2 Evolutionary stages of
massive stars

Figure 24.12 C

24.2 Stellar remnants
 White
•
•

Small (some no larger than Earth)
Dense
•
•
•

•
•

dwarf

Can be more massive than the Sun
Spoonful weighs several tons
Atoms take up less space
• Electrons displaced inward
• Called degenerate matter

Hot surface
Cools to become a black dwarf

24.2 Stellar remnants (continued)
 Neutron
•

Forms from a more massive star
•
•

•
•

star

Star has more gravity
Squeezes itself smaller

Remnant of a supernova
Gravitational force collapses atoms
•
•

Electrons combine with protons to produce
neutrons
Small size

24.2 Stellar remnants (continued)
 Neutron
•

Pea size sample
•
•

•
•

star

Weighs 100 million tons
Same density as an atomic nucleus

Strong magnetic field
First one discovered in early 1970s
•
•

Pulsar (pulsating radio source)
Found in the Crab nebula (remnant of an A.D.
1054 supernova)

Crab Nebula in the
constellation Taurus

Figure 24.14

24.2 Stellar remnants (continued)
 Black
•
•

•

More dense than a neutron star
Intense surface gravity lets no light escape
As matter is pulled into it
•
•

•

hole

Becomes very hot
Emits x-rays

Likely candidate is Cygnus X-1, a strong xray source

Quiz Break

24.3 Galaxies
 Milky
•

Way galaxy

Structure
•
•

•
•

Determined by using radio telescopes
Large spiral galaxy
• About 100,000 light-years wide
• Thickness at the galactic nucleus is about
10,000 light-years
Three spiral arms of stars
Sun is 30,000 light-years from the center

Face-on view of the
Milk Way Galaxy

Figure 24.18 A

Edge-on view of the
Milk Way Galaxy

Figure 24.18 B

24.3 Galaxies (continued)
 Milky
•

Rotation
•
•
•

•

Way galaxy

Around the galactic nucleus
Outermost stars move the slowest
Sun rotates around the galactic nucleus once
about every 200 million years

Halo surrounds the galactic disk
•
•
•

Spherical
Very tenuous gas
Numerous globular clusters

24.3 Galaxies (continued)
 Other
•
•

galaxies

Existence was first proposed in mid-1700s
by Immanuel Kant
Four basic types of galaxies
•

Spiral galaxy
• Arms extending from nucleus
• About 30% of all galaxies
• Large diameter of 20,000 to 125,000 light
years
• Contains both young and old stars
• e.g., Milky Way

Great Galaxy, a spiral galaxy, in
the constellation Andromeda

Figure 24.20

24.3 Galaxies (continued)
 Other
•

galaxies

Four basic types of galaxies
•

•

Barred spiral galaxy
• Stars arranged in the shape of a bar
• Generally quite large
• About 10% of all galaxies
Elliptical galaxy
• Ellipsoidal shape
• About 60% of all galaxies
• Most are smaller than spiral galaxies;
however, they are also the largest known
galaxies

A barred spiral galaxy

Figure 24.22

24.3 Galaxies (continued)
 Other
•

galaxies

Four basic types of galaxies
•

Irregular galaxy
• Lacks symmetry
• About 10% of all galaxies
• Contains mostly young stars
• e.g., Magellanic Clouds

24.3 Galaxies (continued)
 Galactic
•
•
•

Group of galaxies
Some contain thousands of galaxies
Local Group
•
•

•

cluster

Our own group of galaxies
Contains at least 28 galaxies

Supercluster
•
•

Huge swarm of galaxies
May be the largest entity in the universe

Quiz Break

24.4 Red shifts
 Doppler
•

effect

Change in the wavelength of light emitted
by an object due to its motion
•

•

Movement away stretches the wavelength
• Longer wavelength
• Light appears redder
Movement toward “squeezes” the wavelength
• Shorter wavelength
• Light shifted toward the blue

24.4 Red shifts (continued)
 Doppler
•

effect

Amount of the Doppler shift indicates the
rate of movement
•
•

Large Doppler shift indicates a high velocity
Small Doppler shift indicates a lower velocity

 Expanding
•

universe

Most galaxies exhibit a red Doppler shift
•

Moving away

Raisin bread analogy of an
expanding universe

Figure 24.24

24.4 Red shifts (continued)
 Expanding
•

universe

Most galaxies exhibit a red Doppler shift
•

•
•
•

Far galaxies
• Exhibit the greatest shift
• Greater velocity
Discovered in 1929 by Edwin Hubble
Hubble's Law – the recessional speed of
galaxies is proportional to their distance
Accounts for red shifts

24.4 Big Bang theory
 Accounts

for galaxies moving away

from us
 Universe was once confined to a "ball"
that was
•
•

•

Supermassive
Dense
Hot

24.4 Big Bang theory (continued)
 Big

Bang marks the inception of the
universe
•
•

Occurred about 15 billion years ago
All matter and space was created

 Matter

is moving outward
 Fate of the universe
•

Two possibilities
•
•

Universe will last forever
Outward expansion sill stop and gravitational;
contraction will follow

24.4 Big Bang theory (continued)
 Fate
•

of the universe

Final fate depends on the average density
of the universe
•
•

If the density is more than the critical density,
then the universe would contract
Current estimates point to less then the critical
density and predict an ever-expanding, or
open, universe

Chapter 24Test Guidance
You will be responsible on the test for answering 3 of the following 6
questions.
1.

2.

3.
4.
5.
6.

What causes the difference between a star’s apparent
magnitude and it absolute magnitude.
List and explain the three factors that control the apparent
brightness of a star as seen from Earth.
Describe how binary stars are used to determine stellar mass.
List and describe the four basic types of galaxies.
What is Hubble’s Law, please explain in detail.
Briefly describe the Big Bang Theory (not the TV show).

End of Chapter 24


Slide 5

Lecture Outlines
PowerPoint

Chapter 24
Earth Science 11e
Tarbuck/Lutgens
Modified for educational
purposes only
By S. Koziol 12-8-2010

© 2006 Pearson Prentice Hall

Earth Science, 11e
Beyond Our
Solar System
Chapter 24

24.1 Properties of stars
 Distance
•
•

Measuring a star's distance can be very
difficult
Stellar parallax
•
•
•

•
•

Used for measuring distance to a star
Apparent shift in a star's position due to the
orbital motion of Earth
Measured as an angle
Near stars have the largest parallax
Largest parallax is less than one second of arc

24. 1 Properties of stars
(continued)

 Distance
•
•

Distances to the stars are very large
Units of measurement
•
•

•

Kilometers or astronomical units are too
cumbersome to use
Light-year is used most often
• Distance that light travels in 1 year
• One light-year is 9.5 trillion km (5.8 trillion
miles)

Other methods for measuring distance are
also used

24. 1 Properties of stars
(continued)

 Stellar
•

Controlled by three factors
•

•
•

•

brightness

Size
Temperature
Distance

Magnitude
•

Measure of a star's brightness

24.1 Properties of stars
(continued)

 Stellar
•

brightness

Magnitude
•

Two types of measurement
• Apparent magnitude
• Brightness when a star is viewed from
Earth
• Decreases with distance
• Numbers are used to designate
magnitudes - dim stars have large
numbers and negative numbers are also
used

24.1 Properties of stars
(continued)

 Stellar
•

brightness

Magnitude
•

Two types of measurement
• Absolute magnitude
• "True" or intrinsic brightness of a star
• Brightness at a standard distance of
32.6 light-years
• Most stars' absolute magnitudes are
between -5 and +15

24.1 Properties of stars
(continued)

 Color
•

Hot star
•

•
•

•

and temperature

Temperature above 30,000 K
Emits short-wavelength light
Appears blue

Cool star
•
•
•

Temperature less than 3000 K
Emits longer-wavelength light
Appears red

24.1 Properties of stars
(continued)

 Color
•

and temperature

Between 5000 and 6000 K
•
•

Stars appear yellow
e.g., Sun

 Binary
•

stars and stellar mass

Binary stars
•

Two stars orbiting one another
• Stars are held together by mutual
gravitation
• Both orbit around a common center of mass

24.1 Properties of stars (continued)
 Binary
•

Binary stars
•

•
•

•

stars and stellar mass

Visual binaries are resolved telescopically
More than 50% of the stars in the universe are
binary stars
Used to determine stellar mass

Stellar mass
•

Determined using binary stars – the center of
mass is closest to the most massive star

Binary stars
orbit each
other around
their common
center of
mass
Figure 24.4

24.1 Properties of stars (continued)
 Binary
•

stars and stellar mass

Stellar mass
•

Mass of most stars is between one-tenth and
fifty times the mass of the Sun

24.1 Hertzsprung-Russell
diagram
 Shows
•
•

the relation between stellar

Brightness (absolute magnitude) and
Temperature

 Diagram

is made by plotting (graphing)
each star's
•
•

Luminosity (brightness) and
Temperature

24.1 Hertzsprung-Russell
diagram (continued)
 Parts
•

Main-sequence stars
•

•
•

•

of an H-R diagram

90% of all stars
Band through the center of the H-R diagram
Sun is in the main-sequence

Giants (or red giants)
•
•
•

Very luminous
Large
Upper-right on the H-R diagram

24.1 Hertzsprung-Russell
diagram (continued)
 Parts
•

Giants (or red giants)
•

•

•

of an H-R diagram

Very large giants are called supergiants
Only a few percent of all stars

White dwarfs
•
•

•
•
•

Fainter than main-sequence stars
Small (approximate the size of Earth)
Lower-central area on the H-R diagram
Not all are white in color
Perhaps 10% of all stars

Idealized HertzsprungRussell diagram

Figure 24.5

Quiz Break

24.2 Variable stars
 Stars

that fluctuate in brightness
 Types of variable stars
•

Pulsating variables
•
•

•

Fluctuate regularly in brightness
Expand and contract in size

Eruptive variables
•
•
•

Explosive event
Sudden brightening
Called a nova

24.2 Interstellar matter
 Between

the stars is "the vacuum of

space"
 Nebula
•
•

Cloud of dust and gases
Two major types of nebulae
•

Bright nebula
• Glows if it close to a very hot star
• Two types of bright nebulae
• Emission nebula
• Reflection nebula

The Orion Nebula is a wellknown emission nebula

Figure 24.8

A faint blue reflection nebula in
the Pleiades star cluster

Figure 24.9

24.2 Interstellar matter (continued)
 Nebula
•

Two major types of nebulae
•

Dark nebula
• Not close to any bright star
• Appear dark
• Contains the material that forms stars and
planets

24.2 Stellar evolution
 Stars

exist because of gravity
 Two opposing forces in a star are
•
•

Gravity – contracts
Thermal nuclear energy – expands

 Stages
•

Birth
•

•
•
•
•

In dark, cool, interstellar clouds
Gravity contracts the cloud
Temperature rises
Radiates long-wavelength (red) light
Becomes a protostar

24.2 Stellar evolution (continued)
 Stages
•

Protostar
•
•
•

•
•
•
•

Gravitational contraction of gaseous cloud
continues
Core reaches 10 million K
Hydrogen nuclei fuse
• Become helium nuclei
• Process is called hydrogen burning
Energy is released
Outward pressure increases
Outward pressure balanced by gravity pulling in
Star becomes a stable main-sequence star

24.2 Stellar evolution (continued)
 Stages
•

Main-sequence stage
•

Stars age at different rates
• Massive stars use fuel faster and exist for
only a few million years
• Small stars use fuel slowly and exist for
perhaps hundreds of billions of years

•

90% of a star's life is in the main-sequence

24.2 Stellar evolution (continued)
 Stages
•

Red giant stage
•
•

•
•
•

Hydrogen burning migrates outward
Star's outer envelope expands
• Surface cools
• Surface becomes red
Core is collapsing as helium is converted to
carbon
Eventually all nuclear fuel is used
Gravity squeezes the star

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Low-mass star
• 0.5 solar mass
• Red giant collapses
• Becomes a white dwarf

24.2 Evolutionary stages of
low mass stars

Figure 24.12 A

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Medium-mass star
• Between 0.5 and 3 solar masses
• Red giant collapses
• Planetary nebula forms
• Becomes a white dwarf

24.2 Evolutionary stages of
medium mass stars

Figure 24.12 B

H-R diagram showing
stellar evolution

Figure 24.11

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Massive star
• Over 3 solar masses
• Short life span
• Terminates in a brilliant explosion called
a supernova
• Interior condenses
• May produce a hot, dense object that is
either a neutron star or a black hole

24.2 Evolutionary stages of
massive stars

Figure 24.12 C

24.2 Stellar remnants
 White
•
•

Small (some no larger than Earth)
Dense
•
•
•

•
•

dwarf

Can be more massive than the Sun
Spoonful weighs several tons
Atoms take up less space
• Electrons displaced inward
• Called degenerate matter

Hot surface
Cools to become a black dwarf

24.2 Stellar remnants (continued)
 Neutron
•

Forms from a more massive star
•
•

•
•

star

Star has more gravity
Squeezes itself smaller

Remnant of a supernova
Gravitational force collapses atoms
•
•

Electrons combine with protons to produce
neutrons
Small size

24.2 Stellar remnants (continued)
 Neutron
•

Pea size sample
•
•

•
•

star

Weighs 100 million tons
Same density as an atomic nucleus

Strong magnetic field
First one discovered in early 1970s
•
•

Pulsar (pulsating radio source)
Found in the Crab nebula (remnant of an A.D.
1054 supernova)

Crab Nebula in the
constellation Taurus

Figure 24.14

24.2 Stellar remnants (continued)
 Black
•
•

•

More dense than a neutron star
Intense surface gravity lets no light escape
As matter is pulled into it
•
•

•

hole

Becomes very hot
Emits x-rays

Likely candidate is Cygnus X-1, a strong xray source

Quiz Break

24.3 Galaxies
 Milky
•

Way galaxy

Structure
•
•

•
•

Determined by using radio telescopes
Large spiral galaxy
• About 100,000 light-years wide
• Thickness at the galactic nucleus is about
10,000 light-years
Three spiral arms of stars
Sun is 30,000 light-years from the center

Face-on view of the
Milk Way Galaxy

Figure 24.18 A

Edge-on view of the
Milk Way Galaxy

Figure 24.18 B

24.3 Galaxies (continued)
 Milky
•

Rotation
•
•
•

•

Way galaxy

Around the galactic nucleus
Outermost stars move the slowest
Sun rotates around the galactic nucleus once
about every 200 million years

Halo surrounds the galactic disk
•
•
•

Spherical
Very tenuous gas
Numerous globular clusters

24.3 Galaxies (continued)
 Other
•
•

galaxies

Existence was first proposed in mid-1700s
by Immanuel Kant
Four basic types of galaxies
•

Spiral galaxy
• Arms extending from nucleus
• About 30% of all galaxies
• Large diameter of 20,000 to 125,000 light
years
• Contains both young and old stars
• e.g., Milky Way

Great Galaxy, a spiral galaxy, in
the constellation Andromeda

Figure 24.20

24.3 Galaxies (continued)
 Other
•

galaxies

Four basic types of galaxies
•

•

Barred spiral galaxy
• Stars arranged in the shape of a bar
• Generally quite large
• About 10% of all galaxies
Elliptical galaxy
• Ellipsoidal shape
• About 60% of all galaxies
• Most are smaller than spiral galaxies;
however, they are also the largest known
galaxies

A barred spiral galaxy

Figure 24.22

24.3 Galaxies (continued)
 Other
•

galaxies

Four basic types of galaxies
•

Irregular galaxy
• Lacks symmetry
• About 10% of all galaxies
• Contains mostly young stars
• e.g., Magellanic Clouds

24.3 Galaxies (continued)
 Galactic
•
•
•

Group of galaxies
Some contain thousands of galaxies
Local Group
•
•

•

cluster

Our own group of galaxies
Contains at least 28 galaxies

Supercluster
•
•

Huge swarm of galaxies
May be the largest entity in the universe

Quiz Break

24.4 Red shifts
 Doppler
•

effect

Change in the wavelength of light emitted
by an object due to its motion
•

•

Movement away stretches the wavelength
• Longer wavelength
• Light appears redder
Movement toward “squeezes” the wavelength
• Shorter wavelength
• Light shifted toward the blue

24.4 Red shifts (continued)
 Doppler
•

effect

Amount of the Doppler shift indicates the
rate of movement
•
•

Large Doppler shift indicates a high velocity
Small Doppler shift indicates a lower velocity

 Expanding
•

universe

Most galaxies exhibit a red Doppler shift
•

Moving away

Raisin bread analogy of an
expanding universe

Figure 24.24

24.4 Red shifts (continued)
 Expanding
•

universe

Most galaxies exhibit a red Doppler shift
•

•
•
•

Far galaxies
• Exhibit the greatest shift
• Greater velocity
Discovered in 1929 by Edwin Hubble
Hubble's Law – the recessional speed of
galaxies is proportional to their distance
Accounts for red shifts

24.4 Big Bang theory
 Accounts

for galaxies moving away

from us
 Universe was once confined to a "ball"
that was
•
•

•

Supermassive
Dense
Hot

24.4 Big Bang theory (continued)
 Big

Bang marks the inception of the
universe
•
•

Occurred about 15 billion years ago
All matter and space was created

 Matter

is moving outward
 Fate of the universe
•

Two possibilities
•
•

Universe will last forever
Outward expansion sill stop and gravitational;
contraction will follow

24.4 Big Bang theory (continued)
 Fate
•

of the universe

Final fate depends on the average density
of the universe
•
•

If the density is more than the critical density,
then the universe would contract
Current estimates point to less then the critical
density and predict an ever-expanding, or
open, universe

Chapter 24Test Guidance
You will be responsible on the test for answering 3 of the following 6
questions.
1.

2.

3.
4.
5.
6.

What causes the difference between a star’s apparent
magnitude and it absolute magnitude.
List and explain the three factors that control the apparent
brightness of a star as seen from Earth.
Describe how binary stars are used to determine stellar mass.
List and describe the four basic types of galaxies.
What is Hubble’s Law, please explain in detail.
Briefly describe the Big Bang Theory (not the TV show).

End of Chapter 24


Slide 6

Lecture Outlines
PowerPoint

Chapter 24
Earth Science 11e
Tarbuck/Lutgens
Modified for educational
purposes only
By S. Koziol 12-8-2010

© 2006 Pearson Prentice Hall

Earth Science, 11e
Beyond Our
Solar System
Chapter 24

24.1 Properties of stars
 Distance
•
•

Measuring a star's distance can be very
difficult
Stellar parallax
•
•
•

•
•

Used for measuring distance to a star
Apparent shift in a star's position due to the
orbital motion of Earth
Measured as an angle
Near stars have the largest parallax
Largest parallax is less than one second of arc

24. 1 Properties of stars
(continued)

 Distance
•
•

Distances to the stars are very large
Units of measurement
•
•

•

Kilometers or astronomical units are too
cumbersome to use
Light-year is used most often
• Distance that light travels in 1 year
• One light-year is 9.5 trillion km (5.8 trillion
miles)

Other methods for measuring distance are
also used

24. 1 Properties of stars
(continued)

 Stellar
•

Controlled by three factors
•

•
•

•

brightness

Size
Temperature
Distance

Magnitude
•

Measure of a star's brightness

24.1 Properties of stars
(continued)

 Stellar
•

brightness

Magnitude
•

Two types of measurement
• Apparent magnitude
• Brightness when a star is viewed from
Earth
• Decreases with distance
• Numbers are used to designate
magnitudes - dim stars have large
numbers and negative numbers are also
used

24.1 Properties of stars
(continued)

 Stellar
•

brightness

Magnitude
•

Two types of measurement
• Absolute magnitude
• "True" or intrinsic brightness of a star
• Brightness at a standard distance of
32.6 light-years
• Most stars' absolute magnitudes are
between -5 and +15

24.1 Properties of stars
(continued)

 Color
•

Hot star
•

•
•

•

and temperature

Temperature above 30,000 K
Emits short-wavelength light
Appears blue

Cool star
•
•
•

Temperature less than 3000 K
Emits longer-wavelength light
Appears red

24.1 Properties of stars
(continued)

 Color
•

and temperature

Between 5000 and 6000 K
•
•

Stars appear yellow
e.g., Sun

 Binary
•

stars and stellar mass

Binary stars
•

Two stars orbiting one another
• Stars are held together by mutual
gravitation
• Both orbit around a common center of mass

24.1 Properties of stars (continued)
 Binary
•

Binary stars
•

•
•

•

stars and stellar mass

Visual binaries are resolved telescopically
More than 50% of the stars in the universe are
binary stars
Used to determine stellar mass

Stellar mass
•

Determined using binary stars – the center of
mass is closest to the most massive star

Binary stars
orbit each
other around
their common
center of
mass
Figure 24.4

24.1 Properties of stars (continued)
 Binary
•

stars and stellar mass

Stellar mass
•

Mass of most stars is between one-tenth and
fifty times the mass of the Sun

24.1 Hertzsprung-Russell
diagram
 Shows
•
•

the relation between stellar

Brightness (absolute magnitude) and
Temperature

 Diagram

is made by plotting (graphing)
each star's
•
•

Luminosity (brightness) and
Temperature

24.1 Hertzsprung-Russell
diagram (continued)
 Parts
•

Main-sequence stars
•

•
•

•

of an H-R diagram

90% of all stars
Band through the center of the H-R diagram
Sun is in the main-sequence

Giants (or red giants)
•
•
•

Very luminous
Large
Upper-right on the H-R diagram

24.1 Hertzsprung-Russell
diagram (continued)
 Parts
•

Giants (or red giants)
•

•

•

of an H-R diagram

Very large giants are called supergiants
Only a few percent of all stars

White dwarfs
•
•

•
•
•

Fainter than main-sequence stars
Small (approximate the size of Earth)
Lower-central area on the H-R diagram
Not all are white in color
Perhaps 10% of all stars

Idealized HertzsprungRussell diagram

Figure 24.5

Quiz Break

24.2 Variable stars
 Stars

that fluctuate in brightness
 Types of variable stars
•

Pulsating variables
•
•

•

Fluctuate regularly in brightness
Expand and contract in size

Eruptive variables
•
•
•

Explosive event
Sudden brightening
Called a nova

24.2 Interstellar matter
 Between

the stars is "the vacuum of

space"
 Nebula
•
•

Cloud of dust and gases
Two major types of nebulae
•

Bright nebula
• Glows if it close to a very hot star
• Two types of bright nebulae
• Emission nebula
• Reflection nebula

The Orion Nebula is a wellknown emission nebula

Figure 24.8

A faint blue reflection nebula in
the Pleiades star cluster

Figure 24.9

24.2 Interstellar matter (continued)
 Nebula
•

Two major types of nebulae
•

Dark nebula
• Not close to any bright star
• Appear dark
• Contains the material that forms stars and
planets

24.2 Stellar evolution
 Stars

exist because of gravity
 Two opposing forces in a star are
•
•

Gravity – contracts
Thermal nuclear energy – expands

 Stages
•

Birth
•

•
•
•
•

In dark, cool, interstellar clouds
Gravity contracts the cloud
Temperature rises
Radiates long-wavelength (red) light
Becomes a protostar

24.2 Stellar evolution (continued)
 Stages
•

Protostar
•
•
•

•
•
•
•

Gravitational contraction of gaseous cloud
continues
Core reaches 10 million K
Hydrogen nuclei fuse
• Become helium nuclei
• Process is called hydrogen burning
Energy is released
Outward pressure increases
Outward pressure balanced by gravity pulling in
Star becomes a stable main-sequence star

24.2 Stellar evolution (continued)
 Stages
•

Main-sequence stage
•

Stars age at different rates
• Massive stars use fuel faster and exist for
only a few million years
• Small stars use fuel slowly and exist for
perhaps hundreds of billions of years

•

90% of a star's life is in the main-sequence

24.2 Stellar evolution (continued)
 Stages
•

Red giant stage
•
•

•
•
•

Hydrogen burning migrates outward
Star's outer envelope expands
• Surface cools
• Surface becomes red
Core is collapsing as helium is converted to
carbon
Eventually all nuclear fuel is used
Gravity squeezes the star

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Low-mass star
• 0.5 solar mass
• Red giant collapses
• Becomes a white dwarf

24.2 Evolutionary stages of
low mass stars

Figure 24.12 A

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Medium-mass star
• Between 0.5 and 3 solar masses
• Red giant collapses
• Planetary nebula forms
• Becomes a white dwarf

24.2 Evolutionary stages of
medium mass stars

Figure 24.12 B

H-R diagram showing
stellar evolution

Figure 24.11

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Massive star
• Over 3 solar masses
• Short life span
• Terminates in a brilliant explosion called
a supernova
• Interior condenses
• May produce a hot, dense object that is
either a neutron star or a black hole

24.2 Evolutionary stages of
massive stars

Figure 24.12 C

24.2 Stellar remnants
 White
•
•

Small (some no larger than Earth)
Dense
•
•
•

•
•

dwarf

Can be more massive than the Sun
Spoonful weighs several tons
Atoms take up less space
• Electrons displaced inward
• Called degenerate matter

Hot surface
Cools to become a black dwarf

24.2 Stellar remnants (continued)
 Neutron
•

Forms from a more massive star
•
•

•
•

star

Star has more gravity
Squeezes itself smaller

Remnant of a supernova
Gravitational force collapses atoms
•
•

Electrons combine with protons to produce
neutrons
Small size

24.2 Stellar remnants (continued)
 Neutron
•

Pea size sample
•
•

•
•

star

Weighs 100 million tons
Same density as an atomic nucleus

Strong magnetic field
First one discovered in early 1970s
•
•

Pulsar (pulsating radio source)
Found in the Crab nebula (remnant of an A.D.
1054 supernova)

Crab Nebula in the
constellation Taurus

Figure 24.14

24.2 Stellar remnants (continued)
 Black
•
•

•

More dense than a neutron star
Intense surface gravity lets no light escape
As matter is pulled into it
•
•

•

hole

Becomes very hot
Emits x-rays

Likely candidate is Cygnus X-1, a strong xray source

Quiz Break

24.3 Galaxies
 Milky
•

Way galaxy

Structure
•
•

•
•

Determined by using radio telescopes
Large spiral galaxy
• About 100,000 light-years wide
• Thickness at the galactic nucleus is about
10,000 light-years
Three spiral arms of stars
Sun is 30,000 light-years from the center

Face-on view of the
Milk Way Galaxy

Figure 24.18 A

Edge-on view of the
Milk Way Galaxy

Figure 24.18 B

24.3 Galaxies (continued)
 Milky
•

Rotation
•
•
•

•

Way galaxy

Around the galactic nucleus
Outermost stars move the slowest
Sun rotates around the galactic nucleus once
about every 200 million years

Halo surrounds the galactic disk
•
•
•

Spherical
Very tenuous gas
Numerous globular clusters

24.3 Galaxies (continued)
 Other
•
•

galaxies

Existence was first proposed in mid-1700s
by Immanuel Kant
Four basic types of galaxies
•

Spiral galaxy
• Arms extending from nucleus
• About 30% of all galaxies
• Large diameter of 20,000 to 125,000 light
years
• Contains both young and old stars
• e.g., Milky Way

Great Galaxy, a spiral galaxy, in
the constellation Andromeda

Figure 24.20

24.3 Galaxies (continued)
 Other
•

galaxies

Four basic types of galaxies
•

•

Barred spiral galaxy
• Stars arranged in the shape of a bar
• Generally quite large
• About 10% of all galaxies
Elliptical galaxy
• Ellipsoidal shape
• About 60% of all galaxies
• Most are smaller than spiral galaxies;
however, they are also the largest known
galaxies

A barred spiral galaxy

Figure 24.22

24.3 Galaxies (continued)
 Other
•

galaxies

Four basic types of galaxies
•

Irregular galaxy
• Lacks symmetry
• About 10% of all galaxies
• Contains mostly young stars
• e.g., Magellanic Clouds

24.3 Galaxies (continued)
 Galactic
•
•
•

Group of galaxies
Some contain thousands of galaxies
Local Group
•
•

•

cluster

Our own group of galaxies
Contains at least 28 galaxies

Supercluster
•
•

Huge swarm of galaxies
May be the largest entity in the universe

Quiz Break

24.4 Red shifts
 Doppler
•

effect

Change in the wavelength of light emitted
by an object due to its motion
•

•

Movement away stretches the wavelength
• Longer wavelength
• Light appears redder
Movement toward “squeezes” the wavelength
• Shorter wavelength
• Light shifted toward the blue

24.4 Red shifts (continued)
 Doppler
•

effect

Amount of the Doppler shift indicates the
rate of movement
•
•

Large Doppler shift indicates a high velocity
Small Doppler shift indicates a lower velocity

 Expanding
•

universe

Most galaxies exhibit a red Doppler shift
•

Moving away

Raisin bread analogy of an
expanding universe

Figure 24.24

24.4 Red shifts (continued)
 Expanding
•

universe

Most galaxies exhibit a red Doppler shift
•

•
•
•

Far galaxies
• Exhibit the greatest shift
• Greater velocity
Discovered in 1929 by Edwin Hubble
Hubble's Law – the recessional speed of
galaxies is proportional to their distance
Accounts for red shifts

24.4 Big Bang theory
 Accounts

for galaxies moving away

from us
 Universe was once confined to a "ball"
that was
•
•

•

Supermassive
Dense
Hot

24.4 Big Bang theory (continued)
 Big

Bang marks the inception of the
universe
•
•

Occurred about 15 billion years ago
All matter and space was created

 Matter

is moving outward
 Fate of the universe
•

Two possibilities
•
•

Universe will last forever
Outward expansion sill stop and gravitational;
contraction will follow

24.4 Big Bang theory (continued)
 Fate
•

of the universe

Final fate depends on the average density
of the universe
•
•

If the density is more than the critical density,
then the universe would contract
Current estimates point to less then the critical
density and predict an ever-expanding, or
open, universe

Chapter 24Test Guidance
You will be responsible on the test for answering 3 of the following 6
questions.
1.

2.

3.
4.
5.
6.

What causes the difference between a star’s apparent
magnitude and it absolute magnitude.
List and explain the three factors that control the apparent
brightness of a star as seen from Earth.
Describe how binary stars are used to determine stellar mass.
List and describe the four basic types of galaxies.
What is Hubble’s Law, please explain in detail.
Briefly describe the Big Bang Theory (not the TV show).

End of Chapter 24


Slide 7

Lecture Outlines
PowerPoint

Chapter 24
Earth Science 11e
Tarbuck/Lutgens
Modified for educational
purposes only
By S. Koziol 12-8-2010

© 2006 Pearson Prentice Hall

Earth Science, 11e
Beyond Our
Solar System
Chapter 24

24.1 Properties of stars
 Distance
•
•

Measuring a star's distance can be very
difficult
Stellar parallax
•
•
•

•
•

Used for measuring distance to a star
Apparent shift in a star's position due to the
orbital motion of Earth
Measured as an angle
Near stars have the largest parallax
Largest parallax is less than one second of arc

24. 1 Properties of stars
(continued)

 Distance
•
•

Distances to the stars are very large
Units of measurement
•
•

•

Kilometers or astronomical units are too
cumbersome to use
Light-year is used most often
• Distance that light travels in 1 year
• One light-year is 9.5 trillion km (5.8 trillion
miles)

Other methods for measuring distance are
also used

24. 1 Properties of stars
(continued)

 Stellar
•

Controlled by three factors
•

•
•

•

brightness

Size
Temperature
Distance

Magnitude
•

Measure of a star's brightness

24.1 Properties of stars
(continued)

 Stellar
•

brightness

Magnitude
•

Two types of measurement
• Apparent magnitude
• Brightness when a star is viewed from
Earth
• Decreases with distance
• Numbers are used to designate
magnitudes - dim stars have large
numbers and negative numbers are also
used

24.1 Properties of stars
(continued)

 Stellar
•

brightness

Magnitude
•

Two types of measurement
• Absolute magnitude
• "True" or intrinsic brightness of a star
• Brightness at a standard distance of
32.6 light-years
• Most stars' absolute magnitudes are
between -5 and +15

24.1 Properties of stars
(continued)

 Color
•

Hot star
•

•
•

•

and temperature

Temperature above 30,000 K
Emits short-wavelength light
Appears blue

Cool star
•
•
•

Temperature less than 3000 K
Emits longer-wavelength light
Appears red

24.1 Properties of stars
(continued)

 Color
•

and temperature

Between 5000 and 6000 K
•
•

Stars appear yellow
e.g., Sun

 Binary
•

stars and stellar mass

Binary stars
•

Two stars orbiting one another
• Stars are held together by mutual
gravitation
• Both orbit around a common center of mass

24.1 Properties of stars (continued)
 Binary
•

Binary stars
•

•
•

•

stars and stellar mass

Visual binaries are resolved telescopically
More than 50% of the stars in the universe are
binary stars
Used to determine stellar mass

Stellar mass
•

Determined using binary stars – the center of
mass is closest to the most massive star

Binary stars
orbit each
other around
their common
center of
mass
Figure 24.4

24.1 Properties of stars (continued)
 Binary
•

stars and stellar mass

Stellar mass
•

Mass of most stars is between one-tenth and
fifty times the mass of the Sun

24.1 Hertzsprung-Russell
diagram
 Shows
•
•

the relation between stellar

Brightness (absolute magnitude) and
Temperature

 Diagram

is made by plotting (graphing)
each star's
•
•

Luminosity (brightness) and
Temperature

24.1 Hertzsprung-Russell
diagram (continued)
 Parts
•

Main-sequence stars
•

•
•

•

of an H-R diagram

90% of all stars
Band through the center of the H-R diagram
Sun is in the main-sequence

Giants (or red giants)
•
•
•

Very luminous
Large
Upper-right on the H-R diagram

24.1 Hertzsprung-Russell
diagram (continued)
 Parts
•

Giants (or red giants)
•

•

•

of an H-R diagram

Very large giants are called supergiants
Only a few percent of all stars

White dwarfs
•
•

•
•
•

Fainter than main-sequence stars
Small (approximate the size of Earth)
Lower-central area on the H-R diagram
Not all are white in color
Perhaps 10% of all stars

Idealized HertzsprungRussell diagram

Figure 24.5

Quiz Break

24.2 Variable stars
 Stars

that fluctuate in brightness
 Types of variable stars
•

Pulsating variables
•
•

•

Fluctuate regularly in brightness
Expand and contract in size

Eruptive variables
•
•
•

Explosive event
Sudden brightening
Called a nova

24.2 Interstellar matter
 Between

the stars is "the vacuum of

space"
 Nebula
•
•

Cloud of dust and gases
Two major types of nebulae
•

Bright nebula
• Glows if it close to a very hot star
• Two types of bright nebulae
• Emission nebula
• Reflection nebula

The Orion Nebula is a wellknown emission nebula

Figure 24.8

A faint blue reflection nebula in
the Pleiades star cluster

Figure 24.9

24.2 Interstellar matter (continued)
 Nebula
•

Two major types of nebulae
•

Dark nebula
• Not close to any bright star
• Appear dark
• Contains the material that forms stars and
planets

24.2 Stellar evolution
 Stars

exist because of gravity
 Two opposing forces in a star are
•
•

Gravity – contracts
Thermal nuclear energy – expands

 Stages
•

Birth
•

•
•
•
•

In dark, cool, interstellar clouds
Gravity contracts the cloud
Temperature rises
Radiates long-wavelength (red) light
Becomes a protostar

24.2 Stellar evolution (continued)
 Stages
•

Protostar
•
•
•

•
•
•
•

Gravitational contraction of gaseous cloud
continues
Core reaches 10 million K
Hydrogen nuclei fuse
• Become helium nuclei
• Process is called hydrogen burning
Energy is released
Outward pressure increases
Outward pressure balanced by gravity pulling in
Star becomes a stable main-sequence star

24.2 Stellar evolution (continued)
 Stages
•

Main-sequence stage
•

Stars age at different rates
• Massive stars use fuel faster and exist for
only a few million years
• Small stars use fuel slowly and exist for
perhaps hundreds of billions of years

•

90% of a star's life is in the main-sequence

24.2 Stellar evolution (continued)
 Stages
•

Red giant stage
•
•

•
•
•

Hydrogen burning migrates outward
Star's outer envelope expands
• Surface cools
• Surface becomes red
Core is collapsing as helium is converted to
carbon
Eventually all nuclear fuel is used
Gravity squeezes the star

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Low-mass star
• 0.5 solar mass
• Red giant collapses
• Becomes a white dwarf

24.2 Evolutionary stages of
low mass stars

Figure 24.12 A

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Medium-mass star
• Between 0.5 and 3 solar masses
• Red giant collapses
• Planetary nebula forms
• Becomes a white dwarf

24.2 Evolutionary stages of
medium mass stars

Figure 24.12 B

H-R diagram showing
stellar evolution

Figure 24.11

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Massive star
• Over 3 solar masses
• Short life span
• Terminates in a brilliant explosion called
a supernova
• Interior condenses
• May produce a hot, dense object that is
either a neutron star or a black hole

24.2 Evolutionary stages of
massive stars

Figure 24.12 C

24.2 Stellar remnants
 White
•
•

Small (some no larger than Earth)
Dense
•
•
•

•
•

dwarf

Can be more massive than the Sun
Spoonful weighs several tons
Atoms take up less space
• Electrons displaced inward
• Called degenerate matter

Hot surface
Cools to become a black dwarf

24.2 Stellar remnants (continued)
 Neutron
•

Forms from a more massive star
•
•

•
•

star

Star has more gravity
Squeezes itself smaller

Remnant of a supernova
Gravitational force collapses atoms
•
•

Electrons combine with protons to produce
neutrons
Small size

24.2 Stellar remnants (continued)
 Neutron
•

Pea size sample
•
•

•
•

star

Weighs 100 million tons
Same density as an atomic nucleus

Strong magnetic field
First one discovered in early 1970s
•
•

Pulsar (pulsating radio source)
Found in the Crab nebula (remnant of an A.D.
1054 supernova)

Crab Nebula in the
constellation Taurus

Figure 24.14

24.2 Stellar remnants (continued)
 Black
•
•

•

More dense than a neutron star
Intense surface gravity lets no light escape
As matter is pulled into it
•
•

•

hole

Becomes very hot
Emits x-rays

Likely candidate is Cygnus X-1, a strong xray source

Quiz Break

24.3 Galaxies
 Milky
•

Way galaxy

Structure
•
•

•
•

Determined by using radio telescopes
Large spiral galaxy
• About 100,000 light-years wide
• Thickness at the galactic nucleus is about
10,000 light-years
Three spiral arms of stars
Sun is 30,000 light-years from the center

Face-on view of the
Milk Way Galaxy

Figure 24.18 A

Edge-on view of the
Milk Way Galaxy

Figure 24.18 B

24.3 Galaxies (continued)
 Milky
•

Rotation
•
•
•

•

Way galaxy

Around the galactic nucleus
Outermost stars move the slowest
Sun rotates around the galactic nucleus once
about every 200 million years

Halo surrounds the galactic disk
•
•
•

Spherical
Very tenuous gas
Numerous globular clusters

24.3 Galaxies (continued)
 Other
•
•

galaxies

Existence was first proposed in mid-1700s
by Immanuel Kant
Four basic types of galaxies
•

Spiral galaxy
• Arms extending from nucleus
• About 30% of all galaxies
• Large diameter of 20,000 to 125,000 light
years
• Contains both young and old stars
• e.g., Milky Way

Great Galaxy, a spiral galaxy, in
the constellation Andromeda

Figure 24.20

24.3 Galaxies (continued)
 Other
•

galaxies

Four basic types of galaxies
•

•

Barred spiral galaxy
• Stars arranged in the shape of a bar
• Generally quite large
• About 10% of all galaxies
Elliptical galaxy
• Ellipsoidal shape
• About 60% of all galaxies
• Most are smaller than spiral galaxies;
however, they are also the largest known
galaxies

A barred spiral galaxy

Figure 24.22

24.3 Galaxies (continued)
 Other
•

galaxies

Four basic types of galaxies
•

Irregular galaxy
• Lacks symmetry
• About 10% of all galaxies
• Contains mostly young stars
• e.g., Magellanic Clouds

24.3 Galaxies (continued)
 Galactic
•
•
•

Group of galaxies
Some contain thousands of galaxies
Local Group
•
•

•

cluster

Our own group of galaxies
Contains at least 28 galaxies

Supercluster
•
•

Huge swarm of galaxies
May be the largest entity in the universe

Quiz Break

24.4 Red shifts
 Doppler
•

effect

Change in the wavelength of light emitted
by an object due to its motion
•

•

Movement away stretches the wavelength
• Longer wavelength
• Light appears redder
Movement toward “squeezes” the wavelength
• Shorter wavelength
• Light shifted toward the blue

24.4 Red shifts (continued)
 Doppler
•

effect

Amount of the Doppler shift indicates the
rate of movement
•
•

Large Doppler shift indicates a high velocity
Small Doppler shift indicates a lower velocity

 Expanding
•

universe

Most galaxies exhibit a red Doppler shift
•

Moving away

Raisin bread analogy of an
expanding universe

Figure 24.24

24.4 Red shifts (continued)
 Expanding
•

universe

Most galaxies exhibit a red Doppler shift
•

•
•
•

Far galaxies
• Exhibit the greatest shift
• Greater velocity
Discovered in 1929 by Edwin Hubble
Hubble's Law – the recessional speed of
galaxies is proportional to their distance
Accounts for red shifts

24.4 Big Bang theory
 Accounts

for galaxies moving away

from us
 Universe was once confined to a "ball"
that was
•
•

•

Supermassive
Dense
Hot

24.4 Big Bang theory (continued)
 Big

Bang marks the inception of the
universe
•
•

Occurred about 15 billion years ago
All matter and space was created

 Matter

is moving outward
 Fate of the universe
•

Two possibilities
•
•

Universe will last forever
Outward expansion sill stop and gravitational;
contraction will follow

24.4 Big Bang theory (continued)
 Fate
•

of the universe

Final fate depends on the average density
of the universe
•
•

If the density is more than the critical density,
then the universe would contract
Current estimates point to less then the critical
density and predict an ever-expanding, or
open, universe

Chapter 24Test Guidance
You will be responsible on the test for answering 3 of the following 6
questions.
1.

2.

3.
4.
5.
6.

What causes the difference between a star’s apparent
magnitude and it absolute magnitude.
List and explain the three factors that control the apparent
brightness of a star as seen from Earth.
Describe how binary stars are used to determine stellar mass.
List and describe the four basic types of galaxies.
What is Hubble’s Law, please explain in detail.
Briefly describe the Big Bang Theory (not the TV show).

End of Chapter 24


Slide 8

Lecture Outlines
PowerPoint

Chapter 24
Earth Science 11e
Tarbuck/Lutgens
Modified for educational
purposes only
By S. Koziol 12-8-2010

© 2006 Pearson Prentice Hall

Earth Science, 11e
Beyond Our
Solar System
Chapter 24

24.1 Properties of stars
 Distance
•
•

Measuring a star's distance can be very
difficult
Stellar parallax
•
•
•

•
•

Used for measuring distance to a star
Apparent shift in a star's position due to the
orbital motion of Earth
Measured as an angle
Near stars have the largest parallax
Largest parallax is less than one second of arc

24. 1 Properties of stars
(continued)

 Distance
•
•

Distances to the stars are very large
Units of measurement
•
•

•

Kilometers or astronomical units are too
cumbersome to use
Light-year is used most often
• Distance that light travels in 1 year
• One light-year is 9.5 trillion km (5.8 trillion
miles)

Other methods for measuring distance are
also used

24. 1 Properties of stars
(continued)

 Stellar
•

Controlled by three factors
•

•
•

•

brightness

Size
Temperature
Distance

Magnitude
•

Measure of a star's brightness

24.1 Properties of stars
(continued)

 Stellar
•

brightness

Magnitude
•

Two types of measurement
• Apparent magnitude
• Brightness when a star is viewed from
Earth
• Decreases with distance
• Numbers are used to designate
magnitudes - dim stars have large
numbers and negative numbers are also
used

24.1 Properties of stars
(continued)

 Stellar
•

brightness

Magnitude
•

Two types of measurement
• Absolute magnitude
• "True" or intrinsic brightness of a star
• Brightness at a standard distance of
32.6 light-years
• Most stars' absolute magnitudes are
between -5 and +15

24.1 Properties of stars
(continued)

 Color
•

Hot star
•

•
•

•

and temperature

Temperature above 30,000 K
Emits short-wavelength light
Appears blue

Cool star
•
•
•

Temperature less than 3000 K
Emits longer-wavelength light
Appears red

24.1 Properties of stars
(continued)

 Color
•

and temperature

Between 5000 and 6000 K
•
•

Stars appear yellow
e.g., Sun

 Binary
•

stars and stellar mass

Binary stars
•

Two stars orbiting one another
• Stars are held together by mutual
gravitation
• Both orbit around a common center of mass

24.1 Properties of stars (continued)
 Binary
•

Binary stars
•

•
•

•

stars and stellar mass

Visual binaries are resolved telescopically
More than 50% of the stars in the universe are
binary stars
Used to determine stellar mass

Stellar mass
•

Determined using binary stars – the center of
mass is closest to the most massive star

Binary stars
orbit each
other around
their common
center of
mass
Figure 24.4

24.1 Properties of stars (continued)
 Binary
•

stars and stellar mass

Stellar mass
•

Mass of most stars is between one-tenth and
fifty times the mass of the Sun

24.1 Hertzsprung-Russell
diagram
 Shows
•
•

the relation between stellar

Brightness (absolute magnitude) and
Temperature

 Diagram

is made by plotting (graphing)
each star's
•
•

Luminosity (brightness) and
Temperature

24.1 Hertzsprung-Russell
diagram (continued)
 Parts
•

Main-sequence stars
•

•
•

•

of an H-R diagram

90% of all stars
Band through the center of the H-R diagram
Sun is in the main-sequence

Giants (or red giants)
•
•
•

Very luminous
Large
Upper-right on the H-R diagram

24.1 Hertzsprung-Russell
diagram (continued)
 Parts
•

Giants (or red giants)
•

•

•

of an H-R diagram

Very large giants are called supergiants
Only a few percent of all stars

White dwarfs
•
•

•
•
•

Fainter than main-sequence stars
Small (approximate the size of Earth)
Lower-central area on the H-R diagram
Not all are white in color
Perhaps 10% of all stars

Idealized HertzsprungRussell diagram

Figure 24.5

Quiz Break

24.2 Variable stars
 Stars

that fluctuate in brightness
 Types of variable stars
•

Pulsating variables
•
•

•

Fluctuate regularly in brightness
Expand and contract in size

Eruptive variables
•
•
•

Explosive event
Sudden brightening
Called a nova

24.2 Interstellar matter
 Between

the stars is "the vacuum of

space"
 Nebula
•
•

Cloud of dust and gases
Two major types of nebulae
•

Bright nebula
• Glows if it close to a very hot star
• Two types of bright nebulae
• Emission nebula
• Reflection nebula

The Orion Nebula is a wellknown emission nebula

Figure 24.8

A faint blue reflection nebula in
the Pleiades star cluster

Figure 24.9

24.2 Interstellar matter (continued)
 Nebula
•

Two major types of nebulae
•

Dark nebula
• Not close to any bright star
• Appear dark
• Contains the material that forms stars and
planets

24.2 Stellar evolution
 Stars

exist because of gravity
 Two opposing forces in a star are
•
•

Gravity – contracts
Thermal nuclear energy – expands

 Stages
•

Birth
•

•
•
•
•

In dark, cool, interstellar clouds
Gravity contracts the cloud
Temperature rises
Radiates long-wavelength (red) light
Becomes a protostar

24.2 Stellar evolution (continued)
 Stages
•

Protostar
•
•
•

•
•
•
•

Gravitational contraction of gaseous cloud
continues
Core reaches 10 million K
Hydrogen nuclei fuse
• Become helium nuclei
• Process is called hydrogen burning
Energy is released
Outward pressure increases
Outward pressure balanced by gravity pulling in
Star becomes a stable main-sequence star

24.2 Stellar evolution (continued)
 Stages
•

Main-sequence stage
•

Stars age at different rates
• Massive stars use fuel faster and exist for
only a few million years
• Small stars use fuel slowly and exist for
perhaps hundreds of billions of years

•

90% of a star's life is in the main-sequence

24.2 Stellar evolution (continued)
 Stages
•

Red giant stage
•
•

•
•
•

Hydrogen burning migrates outward
Star's outer envelope expands
• Surface cools
• Surface becomes red
Core is collapsing as helium is converted to
carbon
Eventually all nuclear fuel is used
Gravity squeezes the star

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Low-mass star
• 0.5 solar mass
• Red giant collapses
• Becomes a white dwarf

24.2 Evolutionary stages of
low mass stars

Figure 24.12 A

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Medium-mass star
• Between 0.5 and 3 solar masses
• Red giant collapses
• Planetary nebula forms
• Becomes a white dwarf

24.2 Evolutionary stages of
medium mass stars

Figure 24.12 B

H-R diagram showing
stellar evolution

Figure 24.11

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Massive star
• Over 3 solar masses
• Short life span
• Terminates in a brilliant explosion called
a supernova
• Interior condenses
• May produce a hot, dense object that is
either a neutron star or a black hole

24.2 Evolutionary stages of
massive stars

Figure 24.12 C

24.2 Stellar remnants
 White
•
•

Small (some no larger than Earth)
Dense
•
•
•

•
•

dwarf

Can be more massive than the Sun
Spoonful weighs several tons
Atoms take up less space
• Electrons displaced inward
• Called degenerate matter

Hot surface
Cools to become a black dwarf

24.2 Stellar remnants (continued)
 Neutron
•

Forms from a more massive star
•
•

•
•

star

Star has more gravity
Squeezes itself smaller

Remnant of a supernova
Gravitational force collapses atoms
•
•

Electrons combine with protons to produce
neutrons
Small size

24.2 Stellar remnants (continued)
 Neutron
•

Pea size sample
•
•

•
•

star

Weighs 100 million tons
Same density as an atomic nucleus

Strong magnetic field
First one discovered in early 1970s
•
•

Pulsar (pulsating radio source)
Found in the Crab nebula (remnant of an A.D.
1054 supernova)

Crab Nebula in the
constellation Taurus

Figure 24.14

24.2 Stellar remnants (continued)
 Black
•
•

•

More dense than a neutron star
Intense surface gravity lets no light escape
As matter is pulled into it
•
•

•

hole

Becomes very hot
Emits x-rays

Likely candidate is Cygnus X-1, a strong xray source

Quiz Break

24.3 Galaxies
 Milky
•

Way galaxy

Structure
•
•

•
•

Determined by using radio telescopes
Large spiral galaxy
• About 100,000 light-years wide
• Thickness at the galactic nucleus is about
10,000 light-years
Three spiral arms of stars
Sun is 30,000 light-years from the center

Face-on view of the
Milk Way Galaxy

Figure 24.18 A

Edge-on view of the
Milk Way Galaxy

Figure 24.18 B

24.3 Galaxies (continued)
 Milky
•

Rotation
•
•
•

•

Way galaxy

Around the galactic nucleus
Outermost stars move the slowest
Sun rotates around the galactic nucleus once
about every 200 million years

Halo surrounds the galactic disk
•
•
•

Spherical
Very tenuous gas
Numerous globular clusters

24.3 Galaxies (continued)
 Other
•
•

galaxies

Existence was first proposed in mid-1700s
by Immanuel Kant
Four basic types of galaxies
•

Spiral galaxy
• Arms extending from nucleus
• About 30% of all galaxies
• Large diameter of 20,000 to 125,000 light
years
• Contains both young and old stars
• e.g., Milky Way

Great Galaxy, a spiral galaxy, in
the constellation Andromeda

Figure 24.20

24.3 Galaxies (continued)
 Other
•

galaxies

Four basic types of galaxies
•

•

Barred spiral galaxy
• Stars arranged in the shape of a bar
• Generally quite large
• About 10% of all galaxies
Elliptical galaxy
• Ellipsoidal shape
• About 60% of all galaxies
• Most are smaller than spiral galaxies;
however, they are also the largest known
galaxies

A barred spiral galaxy

Figure 24.22

24.3 Galaxies (continued)
 Other
•

galaxies

Four basic types of galaxies
•

Irregular galaxy
• Lacks symmetry
• About 10% of all galaxies
• Contains mostly young stars
• e.g., Magellanic Clouds

24.3 Galaxies (continued)
 Galactic
•
•
•

Group of galaxies
Some contain thousands of galaxies
Local Group
•
•

•

cluster

Our own group of galaxies
Contains at least 28 galaxies

Supercluster
•
•

Huge swarm of galaxies
May be the largest entity in the universe

Quiz Break

24.4 Red shifts
 Doppler
•

effect

Change in the wavelength of light emitted
by an object due to its motion
•

•

Movement away stretches the wavelength
• Longer wavelength
• Light appears redder
Movement toward “squeezes” the wavelength
• Shorter wavelength
• Light shifted toward the blue

24.4 Red shifts (continued)
 Doppler
•

effect

Amount of the Doppler shift indicates the
rate of movement
•
•

Large Doppler shift indicates a high velocity
Small Doppler shift indicates a lower velocity

 Expanding
•

universe

Most galaxies exhibit a red Doppler shift
•

Moving away

Raisin bread analogy of an
expanding universe

Figure 24.24

24.4 Red shifts (continued)
 Expanding
•

universe

Most galaxies exhibit a red Doppler shift
•

•
•
•

Far galaxies
• Exhibit the greatest shift
• Greater velocity
Discovered in 1929 by Edwin Hubble
Hubble's Law – the recessional speed of
galaxies is proportional to their distance
Accounts for red shifts

24.4 Big Bang theory
 Accounts

for galaxies moving away

from us
 Universe was once confined to a "ball"
that was
•
•

•

Supermassive
Dense
Hot

24.4 Big Bang theory (continued)
 Big

Bang marks the inception of the
universe
•
•

Occurred about 15 billion years ago
All matter and space was created

 Matter

is moving outward
 Fate of the universe
•

Two possibilities
•
•

Universe will last forever
Outward expansion sill stop and gravitational;
contraction will follow

24.4 Big Bang theory (continued)
 Fate
•

of the universe

Final fate depends on the average density
of the universe
•
•

If the density is more than the critical density,
then the universe would contract
Current estimates point to less then the critical
density and predict an ever-expanding, or
open, universe

Chapter 24Test Guidance
You will be responsible on the test for answering 3 of the following 6
questions.
1.

2.

3.
4.
5.
6.

What causes the difference between a star’s apparent
magnitude and it absolute magnitude.
List and explain the three factors that control the apparent
brightness of a star as seen from Earth.
Describe how binary stars are used to determine stellar mass.
List and describe the four basic types of galaxies.
What is Hubble’s Law, please explain in detail.
Briefly describe the Big Bang Theory (not the TV show).

End of Chapter 24


Slide 9

Lecture Outlines
PowerPoint

Chapter 24
Earth Science 11e
Tarbuck/Lutgens
Modified for educational
purposes only
By S. Koziol 12-8-2010

© 2006 Pearson Prentice Hall

Earth Science, 11e
Beyond Our
Solar System
Chapter 24

24.1 Properties of stars
 Distance
•
•

Measuring a star's distance can be very
difficult
Stellar parallax
•
•
•

•
•

Used for measuring distance to a star
Apparent shift in a star's position due to the
orbital motion of Earth
Measured as an angle
Near stars have the largest parallax
Largest parallax is less than one second of arc

24. 1 Properties of stars
(continued)

 Distance
•
•

Distances to the stars are very large
Units of measurement
•
•

•

Kilometers or astronomical units are too
cumbersome to use
Light-year is used most often
• Distance that light travels in 1 year
• One light-year is 9.5 trillion km (5.8 trillion
miles)

Other methods for measuring distance are
also used

24. 1 Properties of stars
(continued)

 Stellar
•

Controlled by three factors
•

•
•

•

brightness

Size
Temperature
Distance

Magnitude
•

Measure of a star's brightness

24.1 Properties of stars
(continued)

 Stellar
•

brightness

Magnitude
•

Two types of measurement
• Apparent magnitude
• Brightness when a star is viewed from
Earth
• Decreases with distance
• Numbers are used to designate
magnitudes - dim stars have large
numbers and negative numbers are also
used

24.1 Properties of stars
(continued)

 Stellar
•

brightness

Magnitude
•

Two types of measurement
• Absolute magnitude
• "True" or intrinsic brightness of a star
• Brightness at a standard distance of
32.6 light-years
• Most stars' absolute magnitudes are
between -5 and +15

24.1 Properties of stars
(continued)

 Color
•

Hot star
•

•
•

•

and temperature

Temperature above 30,000 K
Emits short-wavelength light
Appears blue

Cool star
•
•
•

Temperature less than 3000 K
Emits longer-wavelength light
Appears red

24.1 Properties of stars
(continued)

 Color
•

and temperature

Between 5000 and 6000 K
•
•

Stars appear yellow
e.g., Sun

 Binary
•

stars and stellar mass

Binary stars
•

Two stars orbiting one another
• Stars are held together by mutual
gravitation
• Both orbit around a common center of mass

24.1 Properties of stars (continued)
 Binary
•

Binary stars
•

•
•

•

stars and stellar mass

Visual binaries are resolved telescopically
More than 50% of the stars in the universe are
binary stars
Used to determine stellar mass

Stellar mass
•

Determined using binary stars – the center of
mass is closest to the most massive star

Binary stars
orbit each
other around
their common
center of
mass
Figure 24.4

24.1 Properties of stars (continued)
 Binary
•

stars and stellar mass

Stellar mass
•

Mass of most stars is between one-tenth and
fifty times the mass of the Sun

24.1 Hertzsprung-Russell
diagram
 Shows
•
•

the relation between stellar

Brightness (absolute magnitude) and
Temperature

 Diagram

is made by plotting (graphing)
each star's
•
•

Luminosity (brightness) and
Temperature

24.1 Hertzsprung-Russell
diagram (continued)
 Parts
•

Main-sequence stars
•

•
•

•

of an H-R diagram

90% of all stars
Band through the center of the H-R diagram
Sun is in the main-sequence

Giants (or red giants)
•
•
•

Very luminous
Large
Upper-right on the H-R diagram

24.1 Hertzsprung-Russell
diagram (continued)
 Parts
•

Giants (or red giants)
•

•

•

of an H-R diagram

Very large giants are called supergiants
Only a few percent of all stars

White dwarfs
•
•

•
•
•

Fainter than main-sequence stars
Small (approximate the size of Earth)
Lower-central area on the H-R diagram
Not all are white in color
Perhaps 10% of all stars

Idealized HertzsprungRussell diagram

Figure 24.5

Quiz Break

24.2 Variable stars
 Stars

that fluctuate in brightness
 Types of variable stars
•

Pulsating variables
•
•

•

Fluctuate regularly in brightness
Expand and contract in size

Eruptive variables
•
•
•

Explosive event
Sudden brightening
Called a nova

24.2 Interstellar matter
 Between

the stars is "the vacuum of

space"
 Nebula
•
•

Cloud of dust and gases
Two major types of nebulae
•

Bright nebula
• Glows if it close to a very hot star
• Two types of bright nebulae
• Emission nebula
• Reflection nebula

The Orion Nebula is a wellknown emission nebula

Figure 24.8

A faint blue reflection nebula in
the Pleiades star cluster

Figure 24.9

24.2 Interstellar matter (continued)
 Nebula
•

Two major types of nebulae
•

Dark nebula
• Not close to any bright star
• Appear dark
• Contains the material that forms stars and
planets

24.2 Stellar evolution
 Stars

exist because of gravity
 Two opposing forces in a star are
•
•

Gravity – contracts
Thermal nuclear energy – expands

 Stages
•

Birth
•

•
•
•
•

In dark, cool, interstellar clouds
Gravity contracts the cloud
Temperature rises
Radiates long-wavelength (red) light
Becomes a protostar

24.2 Stellar evolution (continued)
 Stages
•

Protostar
•
•
•

•
•
•
•

Gravitational contraction of gaseous cloud
continues
Core reaches 10 million K
Hydrogen nuclei fuse
• Become helium nuclei
• Process is called hydrogen burning
Energy is released
Outward pressure increases
Outward pressure balanced by gravity pulling in
Star becomes a stable main-sequence star

24.2 Stellar evolution (continued)
 Stages
•

Main-sequence stage
•

Stars age at different rates
• Massive stars use fuel faster and exist for
only a few million years
• Small stars use fuel slowly and exist for
perhaps hundreds of billions of years

•

90% of a star's life is in the main-sequence

24.2 Stellar evolution (continued)
 Stages
•

Red giant stage
•
•

•
•
•

Hydrogen burning migrates outward
Star's outer envelope expands
• Surface cools
• Surface becomes red
Core is collapsing as helium is converted to
carbon
Eventually all nuclear fuel is used
Gravity squeezes the star

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Low-mass star
• 0.5 solar mass
• Red giant collapses
• Becomes a white dwarf

24.2 Evolutionary stages of
low mass stars

Figure 24.12 A

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Medium-mass star
• Between 0.5 and 3 solar masses
• Red giant collapses
• Planetary nebula forms
• Becomes a white dwarf

24.2 Evolutionary stages of
medium mass stars

Figure 24.12 B

H-R diagram showing
stellar evolution

Figure 24.11

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Massive star
• Over 3 solar masses
• Short life span
• Terminates in a brilliant explosion called
a supernova
• Interior condenses
• May produce a hot, dense object that is
either a neutron star or a black hole

24.2 Evolutionary stages of
massive stars

Figure 24.12 C

24.2 Stellar remnants
 White
•
•

Small (some no larger than Earth)
Dense
•
•
•

•
•

dwarf

Can be more massive than the Sun
Spoonful weighs several tons
Atoms take up less space
• Electrons displaced inward
• Called degenerate matter

Hot surface
Cools to become a black dwarf

24.2 Stellar remnants (continued)
 Neutron
•

Forms from a more massive star
•
•

•
•

star

Star has more gravity
Squeezes itself smaller

Remnant of a supernova
Gravitational force collapses atoms
•
•

Electrons combine with protons to produce
neutrons
Small size

24.2 Stellar remnants (continued)
 Neutron
•

Pea size sample
•
•

•
•

star

Weighs 100 million tons
Same density as an atomic nucleus

Strong magnetic field
First one discovered in early 1970s
•
•

Pulsar (pulsating radio source)
Found in the Crab nebula (remnant of an A.D.
1054 supernova)

Crab Nebula in the
constellation Taurus

Figure 24.14

24.2 Stellar remnants (continued)
 Black
•
•

•

More dense than a neutron star
Intense surface gravity lets no light escape
As matter is pulled into it
•
•

•

hole

Becomes very hot
Emits x-rays

Likely candidate is Cygnus X-1, a strong xray source

Quiz Break

24.3 Galaxies
 Milky
•

Way galaxy

Structure
•
•

•
•

Determined by using radio telescopes
Large spiral galaxy
• About 100,000 light-years wide
• Thickness at the galactic nucleus is about
10,000 light-years
Three spiral arms of stars
Sun is 30,000 light-years from the center

Face-on view of the
Milk Way Galaxy

Figure 24.18 A

Edge-on view of the
Milk Way Galaxy

Figure 24.18 B

24.3 Galaxies (continued)
 Milky
•

Rotation
•
•
•

•

Way galaxy

Around the galactic nucleus
Outermost stars move the slowest
Sun rotates around the galactic nucleus once
about every 200 million years

Halo surrounds the galactic disk
•
•
•

Spherical
Very tenuous gas
Numerous globular clusters

24.3 Galaxies (continued)
 Other
•
•

galaxies

Existence was first proposed in mid-1700s
by Immanuel Kant
Four basic types of galaxies
•

Spiral galaxy
• Arms extending from nucleus
• About 30% of all galaxies
• Large diameter of 20,000 to 125,000 light
years
• Contains both young and old stars
• e.g., Milky Way

Great Galaxy, a spiral galaxy, in
the constellation Andromeda

Figure 24.20

24.3 Galaxies (continued)
 Other
•

galaxies

Four basic types of galaxies
•

•

Barred spiral galaxy
• Stars arranged in the shape of a bar
• Generally quite large
• About 10% of all galaxies
Elliptical galaxy
• Ellipsoidal shape
• About 60% of all galaxies
• Most are smaller than spiral galaxies;
however, they are also the largest known
galaxies

A barred spiral galaxy

Figure 24.22

24.3 Galaxies (continued)
 Other
•

galaxies

Four basic types of galaxies
•

Irregular galaxy
• Lacks symmetry
• About 10% of all galaxies
• Contains mostly young stars
• e.g., Magellanic Clouds

24.3 Galaxies (continued)
 Galactic
•
•
•

Group of galaxies
Some contain thousands of galaxies
Local Group
•
•

•

cluster

Our own group of galaxies
Contains at least 28 galaxies

Supercluster
•
•

Huge swarm of galaxies
May be the largest entity in the universe

Quiz Break

24.4 Red shifts
 Doppler
•

effect

Change in the wavelength of light emitted
by an object due to its motion
•

•

Movement away stretches the wavelength
• Longer wavelength
• Light appears redder
Movement toward “squeezes” the wavelength
• Shorter wavelength
• Light shifted toward the blue

24.4 Red shifts (continued)
 Doppler
•

effect

Amount of the Doppler shift indicates the
rate of movement
•
•

Large Doppler shift indicates a high velocity
Small Doppler shift indicates a lower velocity

 Expanding
•

universe

Most galaxies exhibit a red Doppler shift
•

Moving away

Raisin bread analogy of an
expanding universe

Figure 24.24

24.4 Red shifts (continued)
 Expanding
•

universe

Most galaxies exhibit a red Doppler shift
•

•
•
•

Far galaxies
• Exhibit the greatest shift
• Greater velocity
Discovered in 1929 by Edwin Hubble
Hubble's Law – the recessional speed of
galaxies is proportional to their distance
Accounts for red shifts

24.4 Big Bang theory
 Accounts

for galaxies moving away

from us
 Universe was once confined to a "ball"
that was
•
•

•

Supermassive
Dense
Hot

24.4 Big Bang theory (continued)
 Big

Bang marks the inception of the
universe
•
•

Occurred about 15 billion years ago
All matter and space was created

 Matter

is moving outward
 Fate of the universe
•

Two possibilities
•
•

Universe will last forever
Outward expansion sill stop and gravitational;
contraction will follow

24.4 Big Bang theory (continued)
 Fate
•

of the universe

Final fate depends on the average density
of the universe
•
•

If the density is more than the critical density,
then the universe would contract
Current estimates point to less then the critical
density and predict an ever-expanding, or
open, universe

Chapter 24Test Guidance
You will be responsible on the test for answering 3 of the following 6
questions.
1.

2.

3.
4.
5.
6.

What causes the difference between a star’s apparent
magnitude and it absolute magnitude.
List and explain the three factors that control the apparent
brightness of a star as seen from Earth.
Describe how binary stars are used to determine stellar mass.
List and describe the four basic types of galaxies.
What is Hubble’s Law, please explain in detail.
Briefly describe the Big Bang Theory (not the TV show).

End of Chapter 24


Slide 10

Lecture Outlines
PowerPoint

Chapter 24
Earth Science 11e
Tarbuck/Lutgens
Modified for educational
purposes only
By S. Koziol 12-8-2010

© 2006 Pearson Prentice Hall

Earth Science, 11e
Beyond Our
Solar System
Chapter 24

24.1 Properties of stars
 Distance
•
•

Measuring a star's distance can be very
difficult
Stellar parallax
•
•
•

•
•

Used for measuring distance to a star
Apparent shift in a star's position due to the
orbital motion of Earth
Measured as an angle
Near stars have the largest parallax
Largest parallax is less than one second of arc

24. 1 Properties of stars
(continued)

 Distance
•
•

Distances to the stars are very large
Units of measurement
•
•

•

Kilometers or astronomical units are too
cumbersome to use
Light-year is used most often
• Distance that light travels in 1 year
• One light-year is 9.5 trillion km (5.8 trillion
miles)

Other methods for measuring distance are
also used

24. 1 Properties of stars
(continued)

 Stellar
•

Controlled by three factors
•

•
•

•

brightness

Size
Temperature
Distance

Magnitude
•

Measure of a star's brightness

24.1 Properties of stars
(continued)

 Stellar
•

brightness

Magnitude
•

Two types of measurement
• Apparent magnitude
• Brightness when a star is viewed from
Earth
• Decreases with distance
• Numbers are used to designate
magnitudes - dim stars have large
numbers and negative numbers are also
used

24.1 Properties of stars
(continued)

 Stellar
•

brightness

Magnitude
•

Two types of measurement
• Absolute magnitude
• "True" or intrinsic brightness of a star
• Brightness at a standard distance of
32.6 light-years
• Most stars' absolute magnitudes are
between -5 and +15

24.1 Properties of stars
(continued)

 Color
•

Hot star
•

•
•

•

and temperature

Temperature above 30,000 K
Emits short-wavelength light
Appears blue

Cool star
•
•
•

Temperature less than 3000 K
Emits longer-wavelength light
Appears red

24.1 Properties of stars
(continued)

 Color
•

and temperature

Between 5000 and 6000 K
•
•

Stars appear yellow
e.g., Sun

 Binary
•

stars and stellar mass

Binary stars
•

Two stars orbiting one another
• Stars are held together by mutual
gravitation
• Both orbit around a common center of mass

24.1 Properties of stars (continued)
 Binary
•

Binary stars
•

•
•

•

stars and stellar mass

Visual binaries are resolved telescopically
More than 50% of the stars in the universe are
binary stars
Used to determine stellar mass

Stellar mass
•

Determined using binary stars – the center of
mass is closest to the most massive star

Binary stars
orbit each
other around
their common
center of
mass
Figure 24.4

24.1 Properties of stars (continued)
 Binary
•

stars and stellar mass

Stellar mass
•

Mass of most stars is between one-tenth and
fifty times the mass of the Sun

24.1 Hertzsprung-Russell
diagram
 Shows
•
•

the relation between stellar

Brightness (absolute magnitude) and
Temperature

 Diagram

is made by plotting (graphing)
each star's
•
•

Luminosity (brightness) and
Temperature

24.1 Hertzsprung-Russell
diagram (continued)
 Parts
•

Main-sequence stars
•

•
•

•

of an H-R diagram

90% of all stars
Band through the center of the H-R diagram
Sun is in the main-sequence

Giants (or red giants)
•
•
•

Very luminous
Large
Upper-right on the H-R diagram

24.1 Hertzsprung-Russell
diagram (continued)
 Parts
•

Giants (or red giants)
•

•

•

of an H-R diagram

Very large giants are called supergiants
Only a few percent of all stars

White dwarfs
•
•

•
•
•

Fainter than main-sequence stars
Small (approximate the size of Earth)
Lower-central area on the H-R diagram
Not all are white in color
Perhaps 10% of all stars

Idealized HertzsprungRussell diagram

Figure 24.5

Quiz Break

24.2 Variable stars
 Stars

that fluctuate in brightness
 Types of variable stars
•

Pulsating variables
•
•

•

Fluctuate regularly in brightness
Expand and contract in size

Eruptive variables
•
•
•

Explosive event
Sudden brightening
Called a nova

24.2 Interstellar matter
 Between

the stars is "the vacuum of

space"
 Nebula
•
•

Cloud of dust and gases
Two major types of nebulae
•

Bright nebula
• Glows if it close to a very hot star
• Two types of bright nebulae
• Emission nebula
• Reflection nebula

The Orion Nebula is a wellknown emission nebula

Figure 24.8

A faint blue reflection nebula in
the Pleiades star cluster

Figure 24.9

24.2 Interstellar matter (continued)
 Nebula
•

Two major types of nebulae
•

Dark nebula
• Not close to any bright star
• Appear dark
• Contains the material that forms stars and
planets

24.2 Stellar evolution
 Stars

exist because of gravity
 Two opposing forces in a star are
•
•

Gravity – contracts
Thermal nuclear energy – expands

 Stages
•

Birth
•

•
•
•
•

In dark, cool, interstellar clouds
Gravity contracts the cloud
Temperature rises
Radiates long-wavelength (red) light
Becomes a protostar

24.2 Stellar evolution (continued)
 Stages
•

Protostar
•
•
•

•
•
•
•

Gravitational contraction of gaseous cloud
continues
Core reaches 10 million K
Hydrogen nuclei fuse
• Become helium nuclei
• Process is called hydrogen burning
Energy is released
Outward pressure increases
Outward pressure balanced by gravity pulling in
Star becomes a stable main-sequence star

24.2 Stellar evolution (continued)
 Stages
•

Main-sequence stage
•

Stars age at different rates
• Massive stars use fuel faster and exist for
only a few million years
• Small stars use fuel slowly and exist for
perhaps hundreds of billions of years

•

90% of a star's life is in the main-sequence

24.2 Stellar evolution (continued)
 Stages
•

Red giant stage
•
•

•
•
•

Hydrogen burning migrates outward
Star's outer envelope expands
• Surface cools
• Surface becomes red
Core is collapsing as helium is converted to
carbon
Eventually all nuclear fuel is used
Gravity squeezes the star

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Low-mass star
• 0.5 solar mass
• Red giant collapses
• Becomes a white dwarf

24.2 Evolutionary stages of
low mass stars

Figure 24.12 A

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Medium-mass star
• Between 0.5 and 3 solar masses
• Red giant collapses
• Planetary nebula forms
• Becomes a white dwarf

24.2 Evolutionary stages of
medium mass stars

Figure 24.12 B

H-R diagram showing
stellar evolution

Figure 24.11

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Massive star
• Over 3 solar masses
• Short life span
• Terminates in a brilliant explosion called
a supernova
• Interior condenses
• May produce a hot, dense object that is
either a neutron star or a black hole

24.2 Evolutionary stages of
massive stars

Figure 24.12 C

24.2 Stellar remnants
 White
•
•

Small (some no larger than Earth)
Dense
•
•
•

•
•

dwarf

Can be more massive than the Sun
Spoonful weighs several tons
Atoms take up less space
• Electrons displaced inward
• Called degenerate matter

Hot surface
Cools to become a black dwarf

24.2 Stellar remnants (continued)
 Neutron
•

Forms from a more massive star
•
•

•
•

star

Star has more gravity
Squeezes itself smaller

Remnant of a supernova
Gravitational force collapses atoms
•
•

Electrons combine with protons to produce
neutrons
Small size

24.2 Stellar remnants (continued)
 Neutron
•

Pea size sample
•
•

•
•

star

Weighs 100 million tons
Same density as an atomic nucleus

Strong magnetic field
First one discovered in early 1970s
•
•

Pulsar (pulsating radio source)
Found in the Crab nebula (remnant of an A.D.
1054 supernova)

Crab Nebula in the
constellation Taurus

Figure 24.14

24.2 Stellar remnants (continued)
 Black
•
•

•

More dense than a neutron star
Intense surface gravity lets no light escape
As matter is pulled into it
•
•

•

hole

Becomes very hot
Emits x-rays

Likely candidate is Cygnus X-1, a strong xray source

Quiz Break

24.3 Galaxies
 Milky
•

Way galaxy

Structure
•
•

•
•

Determined by using radio telescopes
Large spiral galaxy
• About 100,000 light-years wide
• Thickness at the galactic nucleus is about
10,000 light-years
Three spiral arms of stars
Sun is 30,000 light-years from the center

Face-on view of the
Milk Way Galaxy

Figure 24.18 A

Edge-on view of the
Milk Way Galaxy

Figure 24.18 B

24.3 Galaxies (continued)
 Milky
•

Rotation
•
•
•

•

Way galaxy

Around the galactic nucleus
Outermost stars move the slowest
Sun rotates around the galactic nucleus once
about every 200 million years

Halo surrounds the galactic disk
•
•
•

Spherical
Very tenuous gas
Numerous globular clusters

24.3 Galaxies (continued)
 Other
•
•

galaxies

Existence was first proposed in mid-1700s
by Immanuel Kant
Four basic types of galaxies
•

Spiral galaxy
• Arms extending from nucleus
• About 30% of all galaxies
• Large diameter of 20,000 to 125,000 light
years
• Contains both young and old stars
• e.g., Milky Way

Great Galaxy, a spiral galaxy, in
the constellation Andromeda

Figure 24.20

24.3 Galaxies (continued)
 Other
•

galaxies

Four basic types of galaxies
•

•

Barred spiral galaxy
• Stars arranged in the shape of a bar
• Generally quite large
• About 10% of all galaxies
Elliptical galaxy
• Ellipsoidal shape
• About 60% of all galaxies
• Most are smaller than spiral galaxies;
however, they are also the largest known
galaxies

A barred spiral galaxy

Figure 24.22

24.3 Galaxies (continued)
 Other
•

galaxies

Four basic types of galaxies
•

Irregular galaxy
• Lacks symmetry
• About 10% of all galaxies
• Contains mostly young stars
• e.g., Magellanic Clouds

24.3 Galaxies (continued)
 Galactic
•
•
•

Group of galaxies
Some contain thousands of galaxies
Local Group
•
•

•

cluster

Our own group of galaxies
Contains at least 28 galaxies

Supercluster
•
•

Huge swarm of galaxies
May be the largest entity in the universe

Quiz Break

24.4 Red shifts
 Doppler
•

effect

Change in the wavelength of light emitted
by an object due to its motion
•

•

Movement away stretches the wavelength
• Longer wavelength
• Light appears redder
Movement toward “squeezes” the wavelength
• Shorter wavelength
• Light shifted toward the blue

24.4 Red shifts (continued)
 Doppler
•

effect

Amount of the Doppler shift indicates the
rate of movement
•
•

Large Doppler shift indicates a high velocity
Small Doppler shift indicates a lower velocity

 Expanding
•

universe

Most galaxies exhibit a red Doppler shift
•

Moving away

Raisin bread analogy of an
expanding universe

Figure 24.24

24.4 Red shifts (continued)
 Expanding
•

universe

Most galaxies exhibit a red Doppler shift
•

•
•
•

Far galaxies
• Exhibit the greatest shift
• Greater velocity
Discovered in 1929 by Edwin Hubble
Hubble's Law – the recessional speed of
galaxies is proportional to their distance
Accounts for red shifts

24.4 Big Bang theory
 Accounts

for galaxies moving away

from us
 Universe was once confined to a "ball"
that was
•
•

•

Supermassive
Dense
Hot

24.4 Big Bang theory (continued)
 Big

Bang marks the inception of the
universe
•
•

Occurred about 15 billion years ago
All matter and space was created

 Matter

is moving outward
 Fate of the universe
•

Two possibilities
•
•

Universe will last forever
Outward expansion sill stop and gravitational;
contraction will follow

24.4 Big Bang theory (continued)
 Fate
•

of the universe

Final fate depends on the average density
of the universe
•
•

If the density is more than the critical density,
then the universe would contract
Current estimates point to less then the critical
density and predict an ever-expanding, or
open, universe

Chapter 24Test Guidance
You will be responsible on the test for answering 3 of the following 6
questions.
1.

2.

3.
4.
5.
6.

What causes the difference between a star’s apparent
magnitude and it absolute magnitude.
List and explain the three factors that control the apparent
brightness of a star as seen from Earth.
Describe how binary stars are used to determine stellar mass.
List and describe the four basic types of galaxies.
What is Hubble’s Law, please explain in detail.
Briefly describe the Big Bang Theory (not the TV show).

End of Chapter 24


Slide 11

Lecture Outlines
PowerPoint

Chapter 24
Earth Science 11e
Tarbuck/Lutgens
Modified for educational
purposes only
By S. Koziol 12-8-2010

© 2006 Pearson Prentice Hall

Earth Science, 11e
Beyond Our
Solar System
Chapter 24

24.1 Properties of stars
 Distance
•
•

Measuring a star's distance can be very
difficult
Stellar parallax
•
•
•

•
•

Used for measuring distance to a star
Apparent shift in a star's position due to the
orbital motion of Earth
Measured as an angle
Near stars have the largest parallax
Largest parallax is less than one second of arc

24. 1 Properties of stars
(continued)

 Distance
•
•

Distances to the stars are very large
Units of measurement
•
•

•

Kilometers or astronomical units are too
cumbersome to use
Light-year is used most often
• Distance that light travels in 1 year
• One light-year is 9.5 trillion km (5.8 trillion
miles)

Other methods for measuring distance are
also used

24. 1 Properties of stars
(continued)

 Stellar
•

Controlled by three factors
•

•
•

•

brightness

Size
Temperature
Distance

Magnitude
•

Measure of a star's brightness

24.1 Properties of stars
(continued)

 Stellar
•

brightness

Magnitude
•

Two types of measurement
• Apparent magnitude
• Brightness when a star is viewed from
Earth
• Decreases with distance
• Numbers are used to designate
magnitudes - dim stars have large
numbers and negative numbers are also
used

24.1 Properties of stars
(continued)

 Stellar
•

brightness

Magnitude
•

Two types of measurement
• Absolute magnitude
• "True" or intrinsic brightness of a star
• Brightness at a standard distance of
32.6 light-years
• Most stars' absolute magnitudes are
between -5 and +15

24.1 Properties of stars
(continued)

 Color
•

Hot star
•

•
•

•

and temperature

Temperature above 30,000 K
Emits short-wavelength light
Appears blue

Cool star
•
•
•

Temperature less than 3000 K
Emits longer-wavelength light
Appears red

24.1 Properties of stars
(continued)

 Color
•

and temperature

Between 5000 and 6000 K
•
•

Stars appear yellow
e.g., Sun

 Binary
•

stars and stellar mass

Binary stars
•

Two stars orbiting one another
• Stars are held together by mutual
gravitation
• Both orbit around a common center of mass

24.1 Properties of stars (continued)
 Binary
•

Binary stars
•

•
•

•

stars and stellar mass

Visual binaries are resolved telescopically
More than 50% of the stars in the universe are
binary stars
Used to determine stellar mass

Stellar mass
•

Determined using binary stars – the center of
mass is closest to the most massive star

Binary stars
orbit each
other around
their common
center of
mass
Figure 24.4

24.1 Properties of stars (continued)
 Binary
•

stars and stellar mass

Stellar mass
•

Mass of most stars is between one-tenth and
fifty times the mass of the Sun

24.1 Hertzsprung-Russell
diagram
 Shows
•
•

the relation between stellar

Brightness (absolute magnitude) and
Temperature

 Diagram

is made by plotting (graphing)
each star's
•
•

Luminosity (brightness) and
Temperature

24.1 Hertzsprung-Russell
diagram (continued)
 Parts
•

Main-sequence stars
•

•
•

•

of an H-R diagram

90% of all stars
Band through the center of the H-R diagram
Sun is in the main-sequence

Giants (or red giants)
•
•
•

Very luminous
Large
Upper-right on the H-R diagram

24.1 Hertzsprung-Russell
diagram (continued)
 Parts
•

Giants (or red giants)
•

•

•

of an H-R diagram

Very large giants are called supergiants
Only a few percent of all stars

White dwarfs
•
•

•
•
•

Fainter than main-sequence stars
Small (approximate the size of Earth)
Lower-central area on the H-R diagram
Not all are white in color
Perhaps 10% of all stars

Idealized HertzsprungRussell diagram

Figure 24.5

Quiz Break

24.2 Variable stars
 Stars

that fluctuate in brightness
 Types of variable stars
•

Pulsating variables
•
•

•

Fluctuate regularly in brightness
Expand and contract in size

Eruptive variables
•
•
•

Explosive event
Sudden brightening
Called a nova

24.2 Interstellar matter
 Between

the stars is "the vacuum of

space"
 Nebula
•
•

Cloud of dust and gases
Two major types of nebulae
•

Bright nebula
• Glows if it close to a very hot star
• Two types of bright nebulae
• Emission nebula
• Reflection nebula

The Orion Nebula is a wellknown emission nebula

Figure 24.8

A faint blue reflection nebula in
the Pleiades star cluster

Figure 24.9

24.2 Interstellar matter (continued)
 Nebula
•

Two major types of nebulae
•

Dark nebula
• Not close to any bright star
• Appear dark
• Contains the material that forms stars and
planets

24.2 Stellar evolution
 Stars

exist because of gravity
 Two opposing forces in a star are
•
•

Gravity – contracts
Thermal nuclear energy – expands

 Stages
•

Birth
•

•
•
•
•

In dark, cool, interstellar clouds
Gravity contracts the cloud
Temperature rises
Radiates long-wavelength (red) light
Becomes a protostar

24.2 Stellar evolution (continued)
 Stages
•

Protostar
•
•
•

•
•
•
•

Gravitational contraction of gaseous cloud
continues
Core reaches 10 million K
Hydrogen nuclei fuse
• Become helium nuclei
• Process is called hydrogen burning
Energy is released
Outward pressure increases
Outward pressure balanced by gravity pulling in
Star becomes a stable main-sequence star

24.2 Stellar evolution (continued)
 Stages
•

Main-sequence stage
•

Stars age at different rates
• Massive stars use fuel faster and exist for
only a few million years
• Small stars use fuel slowly and exist for
perhaps hundreds of billions of years

•

90% of a star's life is in the main-sequence

24.2 Stellar evolution (continued)
 Stages
•

Red giant stage
•
•

•
•
•

Hydrogen burning migrates outward
Star's outer envelope expands
• Surface cools
• Surface becomes red
Core is collapsing as helium is converted to
carbon
Eventually all nuclear fuel is used
Gravity squeezes the star

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Low-mass star
• 0.5 solar mass
• Red giant collapses
• Becomes a white dwarf

24.2 Evolutionary stages of
low mass stars

Figure 24.12 A

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Medium-mass star
• Between 0.5 and 3 solar masses
• Red giant collapses
• Planetary nebula forms
• Becomes a white dwarf

24.2 Evolutionary stages of
medium mass stars

Figure 24.12 B

H-R diagram showing
stellar evolution

Figure 24.11

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Massive star
• Over 3 solar masses
• Short life span
• Terminates in a brilliant explosion called
a supernova
• Interior condenses
• May produce a hot, dense object that is
either a neutron star or a black hole

24.2 Evolutionary stages of
massive stars

Figure 24.12 C

24.2 Stellar remnants
 White
•
•

Small (some no larger than Earth)
Dense
•
•
•

•
•

dwarf

Can be more massive than the Sun
Spoonful weighs several tons
Atoms take up less space
• Electrons displaced inward
• Called degenerate matter

Hot surface
Cools to become a black dwarf

24.2 Stellar remnants (continued)
 Neutron
•

Forms from a more massive star
•
•

•
•

star

Star has more gravity
Squeezes itself smaller

Remnant of a supernova
Gravitational force collapses atoms
•
•

Electrons combine with protons to produce
neutrons
Small size

24.2 Stellar remnants (continued)
 Neutron
•

Pea size sample
•
•

•
•

star

Weighs 100 million tons
Same density as an atomic nucleus

Strong magnetic field
First one discovered in early 1970s
•
•

Pulsar (pulsating radio source)
Found in the Crab nebula (remnant of an A.D.
1054 supernova)

Crab Nebula in the
constellation Taurus

Figure 24.14

24.2 Stellar remnants (continued)
 Black
•
•

•

More dense than a neutron star
Intense surface gravity lets no light escape
As matter is pulled into it
•
•

•

hole

Becomes very hot
Emits x-rays

Likely candidate is Cygnus X-1, a strong xray source

Quiz Break

24.3 Galaxies
 Milky
•

Way galaxy

Structure
•
•

•
•

Determined by using radio telescopes
Large spiral galaxy
• About 100,000 light-years wide
• Thickness at the galactic nucleus is about
10,000 light-years
Three spiral arms of stars
Sun is 30,000 light-years from the center

Face-on view of the
Milk Way Galaxy

Figure 24.18 A

Edge-on view of the
Milk Way Galaxy

Figure 24.18 B

24.3 Galaxies (continued)
 Milky
•

Rotation
•
•
•

•

Way galaxy

Around the galactic nucleus
Outermost stars move the slowest
Sun rotates around the galactic nucleus once
about every 200 million years

Halo surrounds the galactic disk
•
•
•

Spherical
Very tenuous gas
Numerous globular clusters

24.3 Galaxies (continued)
 Other
•
•

galaxies

Existence was first proposed in mid-1700s
by Immanuel Kant
Four basic types of galaxies
•

Spiral galaxy
• Arms extending from nucleus
• About 30% of all galaxies
• Large diameter of 20,000 to 125,000 light
years
• Contains both young and old stars
• e.g., Milky Way

Great Galaxy, a spiral galaxy, in
the constellation Andromeda

Figure 24.20

24.3 Galaxies (continued)
 Other
•

galaxies

Four basic types of galaxies
•

•

Barred spiral galaxy
• Stars arranged in the shape of a bar
• Generally quite large
• About 10% of all galaxies
Elliptical galaxy
• Ellipsoidal shape
• About 60% of all galaxies
• Most are smaller than spiral galaxies;
however, they are also the largest known
galaxies

A barred spiral galaxy

Figure 24.22

24.3 Galaxies (continued)
 Other
•

galaxies

Four basic types of galaxies
•

Irregular galaxy
• Lacks symmetry
• About 10% of all galaxies
• Contains mostly young stars
• e.g., Magellanic Clouds

24.3 Galaxies (continued)
 Galactic
•
•
•

Group of galaxies
Some contain thousands of galaxies
Local Group
•
•

•

cluster

Our own group of galaxies
Contains at least 28 galaxies

Supercluster
•
•

Huge swarm of galaxies
May be the largest entity in the universe

Quiz Break

24.4 Red shifts
 Doppler
•

effect

Change in the wavelength of light emitted
by an object due to its motion
•

•

Movement away stretches the wavelength
• Longer wavelength
• Light appears redder
Movement toward “squeezes” the wavelength
• Shorter wavelength
• Light shifted toward the blue

24.4 Red shifts (continued)
 Doppler
•

effect

Amount of the Doppler shift indicates the
rate of movement
•
•

Large Doppler shift indicates a high velocity
Small Doppler shift indicates a lower velocity

 Expanding
•

universe

Most galaxies exhibit a red Doppler shift
•

Moving away

Raisin bread analogy of an
expanding universe

Figure 24.24

24.4 Red shifts (continued)
 Expanding
•

universe

Most galaxies exhibit a red Doppler shift
•

•
•
•

Far galaxies
• Exhibit the greatest shift
• Greater velocity
Discovered in 1929 by Edwin Hubble
Hubble's Law – the recessional speed of
galaxies is proportional to their distance
Accounts for red shifts

24.4 Big Bang theory
 Accounts

for galaxies moving away

from us
 Universe was once confined to a "ball"
that was
•
•

•

Supermassive
Dense
Hot

24.4 Big Bang theory (continued)
 Big

Bang marks the inception of the
universe
•
•

Occurred about 15 billion years ago
All matter and space was created

 Matter

is moving outward
 Fate of the universe
•

Two possibilities
•
•

Universe will last forever
Outward expansion sill stop and gravitational;
contraction will follow

24.4 Big Bang theory (continued)
 Fate
•

of the universe

Final fate depends on the average density
of the universe
•
•

If the density is more than the critical density,
then the universe would contract
Current estimates point to less then the critical
density and predict an ever-expanding, or
open, universe

Chapter 24Test Guidance
You will be responsible on the test for answering 3 of the following 6
questions.
1.

2.

3.
4.
5.
6.

What causes the difference between a star’s apparent
magnitude and it absolute magnitude.
List and explain the three factors that control the apparent
brightness of a star as seen from Earth.
Describe how binary stars are used to determine stellar mass.
List and describe the four basic types of galaxies.
What is Hubble’s Law, please explain in detail.
Briefly describe the Big Bang Theory (not the TV show).

End of Chapter 24


Slide 12

Lecture Outlines
PowerPoint

Chapter 24
Earth Science 11e
Tarbuck/Lutgens
Modified for educational
purposes only
By S. Koziol 12-8-2010

© 2006 Pearson Prentice Hall

Earth Science, 11e
Beyond Our
Solar System
Chapter 24

24.1 Properties of stars
 Distance
•
•

Measuring a star's distance can be very
difficult
Stellar parallax
•
•
•

•
•

Used for measuring distance to a star
Apparent shift in a star's position due to the
orbital motion of Earth
Measured as an angle
Near stars have the largest parallax
Largest parallax is less than one second of arc

24. 1 Properties of stars
(continued)

 Distance
•
•

Distances to the stars are very large
Units of measurement
•
•

•

Kilometers or astronomical units are too
cumbersome to use
Light-year is used most often
• Distance that light travels in 1 year
• One light-year is 9.5 trillion km (5.8 trillion
miles)

Other methods for measuring distance are
also used

24. 1 Properties of stars
(continued)

 Stellar
•

Controlled by three factors
•

•
•

•

brightness

Size
Temperature
Distance

Magnitude
•

Measure of a star's brightness

24.1 Properties of stars
(continued)

 Stellar
•

brightness

Magnitude
•

Two types of measurement
• Apparent magnitude
• Brightness when a star is viewed from
Earth
• Decreases with distance
• Numbers are used to designate
magnitudes - dim stars have large
numbers and negative numbers are also
used

24.1 Properties of stars
(continued)

 Stellar
•

brightness

Magnitude
•

Two types of measurement
• Absolute magnitude
• "True" or intrinsic brightness of a star
• Brightness at a standard distance of
32.6 light-years
• Most stars' absolute magnitudes are
between -5 and +15

24.1 Properties of stars
(continued)

 Color
•

Hot star
•

•
•

•

and temperature

Temperature above 30,000 K
Emits short-wavelength light
Appears blue

Cool star
•
•
•

Temperature less than 3000 K
Emits longer-wavelength light
Appears red

24.1 Properties of stars
(continued)

 Color
•

and temperature

Between 5000 and 6000 K
•
•

Stars appear yellow
e.g., Sun

 Binary
•

stars and stellar mass

Binary stars
•

Two stars orbiting one another
• Stars are held together by mutual
gravitation
• Both orbit around a common center of mass

24.1 Properties of stars (continued)
 Binary
•

Binary stars
•

•
•

•

stars and stellar mass

Visual binaries are resolved telescopically
More than 50% of the stars in the universe are
binary stars
Used to determine stellar mass

Stellar mass
•

Determined using binary stars – the center of
mass is closest to the most massive star

Binary stars
orbit each
other around
their common
center of
mass
Figure 24.4

24.1 Properties of stars (continued)
 Binary
•

stars and stellar mass

Stellar mass
•

Mass of most stars is between one-tenth and
fifty times the mass of the Sun

24.1 Hertzsprung-Russell
diagram
 Shows
•
•

the relation between stellar

Brightness (absolute magnitude) and
Temperature

 Diagram

is made by plotting (graphing)
each star's
•
•

Luminosity (brightness) and
Temperature

24.1 Hertzsprung-Russell
diagram (continued)
 Parts
•

Main-sequence stars
•

•
•

•

of an H-R diagram

90% of all stars
Band through the center of the H-R diagram
Sun is in the main-sequence

Giants (or red giants)
•
•
•

Very luminous
Large
Upper-right on the H-R diagram

24.1 Hertzsprung-Russell
diagram (continued)
 Parts
•

Giants (or red giants)
•

•

•

of an H-R diagram

Very large giants are called supergiants
Only a few percent of all stars

White dwarfs
•
•

•
•
•

Fainter than main-sequence stars
Small (approximate the size of Earth)
Lower-central area on the H-R diagram
Not all are white in color
Perhaps 10% of all stars

Idealized HertzsprungRussell diagram

Figure 24.5

Quiz Break

24.2 Variable stars
 Stars

that fluctuate in brightness
 Types of variable stars
•

Pulsating variables
•
•

•

Fluctuate regularly in brightness
Expand and contract in size

Eruptive variables
•
•
•

Explosive event
Sudden brightening
Called a nova

24.2 Interstellar matter
 Between

the stars is "the vacuum of

space"
 Nebula
•
•

Cloud of dust and gases
Two major types of nebulae
•

Bright nebula
• Glows if it close to a very hot star
• Two types of bright nebulae
• Emission nebula
• Reflection nebula

The Orion Nebula is a wellknown emission nebula

Figure 24.8

A faint blue reflection nebula in
the Pleiades star cluster

Figure 24.9

24.2 Interstellar matter (continued)
 Nebula
•

Two major types of nebulae
•

Dark nebula
• Not close to any bright star
• Appear dark
• Contains the material that forms stars and
planets

24.2 Stellar evolution
 Stars

exist because of gravity
 Two opposing forces in a star are
•
•

Gravity – contracts
Thermal nuclear energy – expands

 Stages
•

Birth
•

•
•
•
•

In dark, cool, interstellar clouds
Gravity contracts the cloud
Temperature rises
Radiates long-wavelength (red) light
Becomes a protostar

24.2 Stellar evolution (continued)
 Stages
•

Protostar
•
•
•

•
•
•
•

Gravitational contraction of gaseous cloud
continues
Core reaches 10 million K
Hydrogen nuclei fuse
• Become helium nuclei
• Process is called hydrogen burning
Energy is released
Outward pressure increases
Outward pressure balanced by gravity pulling in
Star becomes a stable main-sequence star

24.2 Stellar evolution (continued)
 Stages
•

Main-sequence stage
•

Stars age at different rates
• Massive stars use fuel faster and exist for
only a few million years
• Small stars use fuel slowly and exist for
perhaps hundreds of billions of years

•

90% of a star's life is in the main-sequence

24.2 Stellar evolution (continued)
 Stages
•

Red giant stage
•
•

•
•
•

Hydrogen burning migrates outward
Star's outer envelope expands
• Surface cools
• Surface becomes red
Core is collapsing as helium is converted to
carbon
Eventually all nuclear fuel is used
Gravity squeezes the star

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Low-mass star
• 0.5 solar mass
• Red giant collapses
• Becomes a white dwarf

24.2 Evolutionary stages of
low mass stars

Figure 24.12 A

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Medium-mass star
• Between 0.5 and 3 solar masses
• Red giant collapses
• Planetary nebula forms
• Becomes a white dwarf

24.2 Evolutionary stages of
medium mass stars

Figure 24.12 B

H-R diagram showing
stellar evolution

Figure 24.11

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Massive star
• Over 3 solar masses
• Short life span
• Terminates in a brilliant explosion called
a supernova
• Interior condenses
• May produce a hot, dense object that is
either a neutron star or a black hole

24.2 Evolutionary stages of
massive stars

Figure 24.12 C

24.2 Stellar remnants
 White
•
•

Small (some no larger than Earth)
Dense
•
•
•

•
•

dwarf

Can be more massive than the Sun
Spoonful weighs several tons
Atoms take up less space
• Electrons displaced inward
• Called degenerate matter

Hot surface
Cools to become a black dwarf

24.2 Stellar remnants (continued)
 Neutron
•

Forms from a more massive star
•
•

•
•

star

Star has more gravity
Squeezes itself smaller

Remnant of a supernova
Gravitational force collapses atoms
•
•

Electrons combine with protons to produce
neutrons
Small size

24.2 Stellar remnants (continued)
 Neutron
•

Pea size sample
•
•

•
•

star

Weighs 100 million tons
Same density as an atomic nucleus

Strong magnetic field
First one discovered in early 1970s
•
•

Pulsar (pulsating radio source)
Found in the Crab nebula (remnant of an A.D.
1054 supernova)

Crab Nebula in the
constellation Taurus

Figure 24.14

24.2 Stellar remnants (continued)
 Black
•
•

•

More dense than a neutron star
Intense surface gravity lets no light escape
As matter is pulled into it
•
•

•

hole

Becomes very hot
Emits x-rays

Likely candidate is Cygnus X-1, a strong xray source

Quiz Break

24.3 Galaxies
 Milky
•

Way galaxy

Structure
•
•

•
•

Determined by using radio telescopes
Large spiral galaxy
• About 100,000 light-years wide
• Thickness at the galactic nucleus is about
10,000 light-years
Three spiral arms of stars
Sun is 30,000 light-years from the center

Face-on view of the
Milk Way Galaxy

Figure 24.18 A

Edge-on view of the
Milk Way Galaxy

Figure 24.18 B

24.3 Galaxies (continued)
 Milky
•

Rotation
•
•
•

•

Way galaxy

Around the galactic nucleus
Outermost stars move the slowest
Sun rotates around the galactic nucleus once
about every 200 million years

Halo surrounds the galactic disk
•
•
•

Spherical
Very tenuous gas
Numerous globular clusters

24.3 Galaxies (continued)
 Other
•
•

galaxies

Existence was first proposed in mid-1700s
by Immanuel Kant
Four basic types of galaxies
•

Spiral galaxy
• Arms extending from nucleus
• About 30% of all galaxies
• Large diameter of 20,000 to 125,000 light
years
• Contains both young and old stars
• e.g., Milky Way

Great Galaxy, a spiral galaxy, in
the constellation Andromeda

Figure 24.20

24.3 Galaxies (continued)
 Other
•

galaxies

Four basic types of galaxies
•

•

Barred spiral galaxy
• Stars arranged in the shape of a bar
• Generally quite large
• About 10% of all galaxies
Elliptical galaxy
• Ellipsoidal shape
• About 60% of all galaxies
• Most are smaller than spiral galaxies;
however, they are also the largest known
galaxies

A barred spiral galaxy

Figure 24.22

24.3 Galaxies (continued)
 Other
•

galaxies

Four basic types of galaxies
•

Irregular galaxy
• Lacks symmetry
• About 10% of all galaxies
• Contains mostly young stars
• e.g., Magellanic Clouds

24.3 Galaxies (continued)
 Galactic
•
•
•

Group of galaxies
Some contain thousands of galaxies
Local Group
•
•

•

cluster

Our own group of galaxies
Contains at least 28 galaxies

Supercluster
•
•

Huge swarm of galaxies
May be the largest entity in the universe

Quiz Break

24.4 Red shifts
 Doppler
•

effect

Change in the wavelength of light emitted
by an object due to its motion
•

•

Movement away stretches the wavelength
• Longer wavelength
• Light appears redder
Movement toward “squeezes” the wavelength
• Shorter wavelength
• Light shifted toward the blue

24.4 Red shifts (continued)
 Doppler
•

effect

Amount of the Doppler shift indicates the
rate of movement
•
•

Large Doppler shift indicates a high velocity
Small Doppler shift indicates a lower velocity

 Expanding
•

universe

Most galaxies exhibit a red Doppler shift
•

Moving away

Raisin bread analogy of an
expanding universe

Figure 24.24

24.4 Red shifts (continued)
 Expanding
•

universe

Most galaxies exhibit a red Doppler shift
•

•
•
•

Far galaxies
• Exhibit the greatest shift
• Greater velocity
Discovered in 1929 by Edwin Hubble
Hubble's Law – the recessional speed of
galaxies is proportional to their distance
Accounts for red shifts

24.4 Big Bang theory
 Accounts

for galaxies moving away

from us
 Universe was once confined to a "ball"
that was
•
•

•

Supermassive
Dense
Hot

24.4 Big Bang theory (continued)
 Big

Bang marks the inception of the
universe
•
•

Occurred about 15 billion years ago
All matter and space was created

 Matter

is moving outward
 Fate of the universe
•

Two possibilities
•
•

Universe will last forever
Outward expansion sill stop and gravitational;
contraction will follow

24.4 Big Bang theory (continued)
 Fate
•

of the universe

Final fate depends on the average density
of the universe
•
•

If the density is more than the critical density,
then the universe would contract
Current estimates point to less then the critical
density and predict an ever-expanding, or
open, universe

Chapter 24Test Guidance
You will be responsible on the test for answering 3 of the following 6
questions.
1.

2.

3.
4.
5.
6.

What causes the difference between a star’s apparent
magnitude and it absolute magnitude.
List and explain the three factors that control the apparent
brightness of a star as seen from Earth.
Describe how binary stars are used to determine stellar mass.
List and describe the four basic types of galaxies.
What is Hubble’s Law, please explain in detail.
Briefly describe the Big Bang Theory (not the TV show).

End of Chapter 24


Slide 13

Lecture Outlines
PowerPoint

Chapter 24
Earth Science 11e
Tarbuck/Lutgens
Modified for educational
purposes only
By S. Koziol 12-8-2010

© 2006 Pearson Prentice Hall

Earth Science, 11e
Beyond Our
Solar System
Chapter 24

24.1 Properties of stars
 Distance
•
•

Measuring a star's distance can be very
difficult
Stellar parallax
•
•
•

•
•

Used for measuring distance to a star
Apparent shift in a star's position due to the
orbital motion of Earth
Measured as an angle
Near stars have the largest parallax
Largest parallax is less than one second of arc

24. 1 Properties of stars
(continued)

 Distance
•
•

Distances to the stars are very large
Units of measurement
•
•

•

Kilometers or astronomical units are too
cumbersome to use
Light-year is used most often
• Distance that light travels in 1 year
• One light-year is 9.5 trillion km (5.8 trillion
miles)

Other methods for measuring distance are
also used

24. 1 Properties of stars
(continued)

 Stellar
•

Controlled by three factors
•

•
•

•

brightness

Size
Temperature
Distance

Magnitude
•

Measure of a star's brightness

24.1 Properties of stars
(continued)

 Stellar
•

brightness

Magnitude
•

Two types of measurement
• Apparent magnitude
• Brightness when a star is viewed from
Earth
• Decreases with distance
• Numbers are used to designate
magnitudes - dim stars have large
numbers and negative numbers are also
used

24.1 Properties of stars
(continued)

 Stellar
•

brightness

Magnitude
•

Two types of measurement
• Absolute magnitude
• "True" or intrinsic brightness of a star
• Brightness at a standard distance of
32.6 light-years
• Most stars' absolute magnitudes are
between -5 and +15

24.1 Properties of stars
(continued)

 Color
•

Hot star
•

•
•

•

and temperature

Temperature above 30,000 K
Emits short-wavelength light
Appears blue

Cool star
•
•
•

Temperature less than 3000 K
Emits longer-wavelength light
Appears red

24.1 Properties of stars
(continued)

 Color
•

and temperature

Between 5000 and 6000 K
•
•

Stars appear yellow
e.g., Sun

 Binary
•

stars and stellar mass

Binary stars
•

Two stars orbiting one another
• Stars are held together by mutual
gravitation
• Both orbit around a common center of mass

24.1 Properties of stars (continued)
 Binary
•

Binary stars
•

•
•

•

stars and stellar mass

Visual binaries are resolved telescopically
More than 50% of the stars in the universe are
binary stars
Used to determine stellar mass

Stellar mass
•

Determined using binary stars – the center of
mass is closest to the most massive star

Binary stars
orbit each
other around
their common
center of
mass
Figure 24.4

24.1 Properties of stars (continued)
 Binary
•

stars and stellar mass

Stellar mass
•

Mass of most stars is between one-tenth and
fifty times the mass of the Sun

24.1 Hertzsprung-Russell
diagram
 Shows
•
•

the relation between stellar

Brightness (absolute magnitude) and
Temperature

 Diagram

is made by plotting (graphing)
each star's
•
•

Luminosity (brightness) and
Temperature

24.1 Hertzsprung-Russell
diagram (continued)
 Parts
•

Main-sequence stars
•

•
•

•

of an H-R diagram

90% of all stars
Band through the center of the H-R diagram
Sun is in the main-sequence

Giants (or red giants)
•
•
•

Very luminous
Large
Upper-right on the H-R diagram

24.1 Hertzsprung-Russell
diagram (continued)
 Parts
•

Giants (or red giants)
•

•

•

of an H-R diagram

Very large giants are called supergiants
Only a few percent of all stars

White dwarfs
•
•

•
•
•

Fainter than main-sequence stars
Small (approximate the size of Earth)
Lower-central area on the H-R diagram
Not all are white in color
Perhaps 10% of all stars

Idealized HertzsprungRussell diagram

Figure 24.5

Quiz Break

24.2 Variable stars
 Stars

that fluctuate in brightness
 Types of variable stars
•

Pulsating variables
•
•

•

Fluctuate regularly in brightness
Expand and contract in size

Eruptive variables
•
•
•

Explosive event
Sudden brightening
Called a nova

24.2 Interstellar matter
 Between

the stars is "the vacuum of

space"
 Nebula
•
•

Cloud of dust and gases
Two major types of nebulae
•

Bright nebula
• Glows if it close to a very hot star
• Two types of bright nebulae
• Emission nebula
• Reflection nebula

The Orion Nebula is a wellknown emission nebula

Figure 24.8

A faint blue reflection nebula in
the Pleiades star cluster

Figure 24.9

24.2 Interstellar matter (continued)
 Nebula
•

Two major types of nebulae
•

Dark nebula
• Not close to any bright star
• Appear dark
• Contains the material that forms stars and
planets

24.2 Stellar evolution
 Stars

exist because of gravity
 Two opposing forces in a star are
•
•

Gravity – contracts
Thermal nuclear energy – expands

 Stages
•

Birth
•

•
•
•
•

In dark, cool, interstellar clouds
Gravity contracts the cloud
Temperature rises
Radiates long-wavelength (red) light
Becomes a protostar

24.2 Stellar evolution (continued)
 Stages
•

Protostar
•
•
•

•
•
•
•

Gravitational contraction of gaseous cloud
continues
Core reaches 10 million K
Hydrogen nuclei fuse
• Become helium nuclei
• Process is called hydrogen burning
Energy is released
Outward pressure increases
Outward pressure balanced by gravity pulling in
Star becomes a stable main-sequence star

24.2 Stellar evolution (continued)
 Stages
•

Main-sequence stage
•

Stars age at different rates
• Massive stars use fuel faster and exist for
only a few million years
• Small stars use fuel slowly and exist for
perhaps hundreds of billions of years

•

90% of a star's life is in the main-sequence

24.2 Stellar evolution (continued)
 Stages
•

Red giant stage
•
•

•
•
•

Hydrogen burning migrates outward
Star's outer envelope expands
• Surface cools
• Surface becomes red
Core is collapsing as helium is converted to
carbon
Eventually all nuclear fuel is used
Gravity squeezes the star

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Low-mass star
• 0.5 solar mass
• Red giant collapses
• Becomes a white dwarf

24.2 Evolutionary stages of
low mass stars

Figure 24.12 A

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Medium-mass star
• Between 0.5 and 3 solar masses
• Red giant collapses
• Planetary nebula forms
• Becomes a white dwarf

24.2 Evolutionary stages of
medium mass stars

Figure 24.12 B

H-R diagram showing
stellar evolution

Figure 24.11

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Massive star
• Over 3 solar masses
• Short life span
• Terminates in a brilliant explosion called
a supernova
• Interior condenses
• May produce a hot, dense object that is
either a neutron star or a black hole

24.2 Evolutionary stages of
massive stars

Figure 24.12 C

24.2 Stellar remnants
 White
•
•

Small (some no larger than Earth)
Dense
•
•
•

•
•

dwarf

Can be more massive than the Sun
Spoonful weighs several tons
Atoms take up less space
• Electrons displaced inward
• Called degenerate matter

Hot surface
Cools to become a black dwarf

24.2 Stellar remnants (continued)
 Neutron
•

Forms from a more massive star
•
•

•
•

star

Star has more gravity
Squeezes itself smaller

Remnant of a supernova
Gravitational force collapses atoms
•
•

Electrons combine with protons to produce
neutrons
Small size

24.2 Stellar remnants (continued)
 Neutron
•

Pea size sample
•
•

•
•

star

Weighs 100 million tons
Same density as an atomic nucleus

Strong magnetic field
First one discovered in early 1970s
•
•

Pulsar (pulsating radio source)
Found in the Crab nebula (remnant of an A.D.
1054 supernova)

Crab Nebula in the
constellation Taurus

Figure 24.14

24.2 Stellar remnants (continued)
 Black
•
•

•

More dense than a neutron star
Intense surface gravity lets no light escape
As matter is pulled into it
•
•

•

hole

Becomes very hot
Emits x-rays

Likely candidate is Cygnus X-1, a strong xray source

Quiz Break

24.3 Galaxies
 Milky
•

Way galaxy

Structure
•
•

•
•

Determined by using radio telescopes
Large spiral galaxy
• About 100,000 light-years wide
• Thickness at the galactic nucleus is about
10,000 light-years
Three spiral arms of stars
Sun is 30,000 light-years from the center

Face-on view of the
Milk Way Galaxy

Figure 24.18 A

Edge-on view of the
Milk Way Galaxy

Figure 24.18 B

24.3 Galaxies (continued)
 Milky
•

Rotation
•
•
•

•

Way galaxy

Around the galactic nucleus
Outermost stars move the slowest
Sun rotates around the galactic nucleus once
about every 200 million years

Halo surrounds the galactic disk
•
•
•

Spherical
Very tenuous gas
Numerous globular clusters

24.3 Galaxies (continued)
 Other
•
•

galaxies

Existence was first proposed in mid-1700s
by Immanuel Kant
Four basic types of galaxies
•

Spiral galaxy
• Arms extending from nucleus
• About 30% of all galaxies
• Large diameter of 20,000 to 125,000 light
years
• Contains both young and old stars
• e.g., Milky Way

Great Galaxy, a spiral galaxy, in
the constellation Andromeda

Figure 24.20

24.3 Galaxies (continued)
 Other
•

galaxies

Four basic types of galaxies
•

•

Barred spiral galaxy
• Stars arranged in the shape of a bar
• Generally quite large
• About 10% of all galaxies
Elliptical galaxy
• Ellipsoidal shape
• About 60% of all galaxies
• Most are smaller than spiral galaxies;
however, they are also the largest known
galaxies

A barred spiral galaxy

Figure 24.22

24.3 Galaxies (continued)
 Other
•

galaxies

Four basic types of galaxies
•

Irregular galaxy
• Lacks symmetry
• About 10% of all galaxies
• Contains mostly young stars
• e.g., Magellanic Clouds

24.3 Galaxies (continued)
 Galactic
•
•
•

Group of galaxies
Some contain thousands of galaxies
Local Group
•
•

•

cluster

Our own group of galaxies
Contains at least 28 galaxies

Supercluster
•
•

Huge swarm of galaxies
May be the largest entity in the universe

Quiz Break

24.4 Red shifts
 Doppler
•

effect

Change in the wavelength of light emitted
by an object due to its motion
•

•

Movement away stretches the wavelength
• Longer wavelength
• Light appears redder
Movement toward “squeezes” the wavelength
• Shorter wavelength
• Light shifted toward the blue

24.4 Red shifts (continued)
 Doppler
•

effect

Amount of the Doppler shift indicates the
rate of movement
•
•

Large Doppler shift indicates a high velocity
Small Doppler shift indicates a lower velocity

 Expanding
•

universe

Most galaxies exhibit a red Doppler shift
•

Moving away

Raisin bread analogy of an
expanding universe

Figure 24.24

24.4 Red shifts (continued)
 Expanding
•

universe

Most galaxies exhibit a red Doppler shift
•

•
•
•

Far galaxies
• Exhibit the greatest shift
• Greater velocity
Discovered in 1929 by Edwin Hubble
Hubble's Law – the recessional speed of
galaxies is proportional to their distance
Accounts for red shifts

24.4 Big Bang theory
 Accounts

for galaxies moving away

from us
 Universe was once confined to a "ball"
that was
•
•

•

Supermassive
Dense
Hot

24.4 Big Bang theory (continued)
 Big

Bang marks the inception of the
universe
•
•

Occurred about 15 billion years ago
All matter and space was created

 Matter

is moving outward
 Fate of the universe
•

Two possibilities
•
•

Universe will last forever
Outward expansion sill stop and gravitational;
contraction will follow

24.4 Big Bang theory (continued)
 Fate
•

of the universe

Final fate depends on the average density
of the universe
•
•

If the density is more than the critical density,
then the universe would contract
Current estimates point to less then the critical
density and predict an ever-expanding, or
open, universe

Chapter 24Test Guidance
You will be responsible on the test for answering 3 of the following 6
questions.
1.

2.

3.
4.
5.
6.

What causes the difference between a star’s apparent
magnitude and it absolute magnitude.
List and explain the three factors that control the apparent
brightness of a star as seen from Earth.
Describe how binary stars are used to determine stellar mass.
List and describe the four basic types of galaxies.
What is Hubble’s Law, please explain in detail.
Briefly describe the Big Bang Theory (not the TV show).

End of Chapter 24


Slide 14

Lecture Outlines
PowerPoint

Chapter 24
Earth Science 11e
Tarbuck/Lutgens
Modified for educational
purposes only
By S. Koziol 12-8-2010

© 2006 Pearson Prentice Hall

Earth Science, 11e
Beyond Our
Solar System
Chapter 24

24.1 Properties of stars
 Distance
•
•

Measuring a star's distance can be very
difficult
Stellar parallax
•
•
•

•
•

Used for measuring distance to a star
Apparent shift in a star's position due to the
orbital motion of Earth
Measured as an angle
Near stars have the largest parallax
Largest parallax is less than one second of arc

24. 1 Properties of stars
(continued)

 Distance
•
•

Distances to the stars are very large
Units of measurement
•
•

•

Kilometers or astronomical units are too
cumbersome to use
Light-year is used most often
• Distance that light travels in 1 year
• One light-year is 9.5 trillion km (5.8 trillion
miles)

Other methods for measuring distance are
also used

24. 1 Properties of stars
(continued)

 Stellar
•

Controlled by three factors
•

•
•

•

brightness

Size
Temperature
Distance

Magnitude
•

Measure of a star's brightness

24.1 Properties of stars
(continued)

 Stellar
•

brightness

Magnitude
•

Two types of measurement
• Apparent magnitude
• Brightness when a star is viewed from
Earth
• Decreases with distance
• Numbers are used to designate
magnitudes - dim stars have large
numbers and negative numbers are also
used

24.1 Properties of stars
(continued)

 Stellar
•

brightness

Magnitude
•

Two types of measurement
• Absolute magnitude
• "True" or intrinsic brightness of a star
• Brightness at a standard distance of
32.6 light-years
• Most stars' absolute magnitudes are
between -5 and +15

24.1 Properties of stars
(continued)

 Color
•

Hot star
•

•
•

•

and temperature

Temperature above 30,000 K
Emits short-wavelength light
Appears blue

Cool star
•
•
•

Temperature less than 3000 K
Emits longer-wavelength light
Appears red

24.1 Properties of stars
(continued)

 Color
•

and temperature

Between 5000 and 6000 K
•
•

Stars appear yellow
e.g., Sun

 Binary
•

stars and stellar mass

Binary stars
•

Two stars orbiting one another
• Stars are held together by mutual
gravitation
• Both orbit around a common center of mass

24.1 Properties of stars (continued)
 Binary
•

Binary stars
•

•
•

•

stars and stellar mass

Visual binaries are resolved telescopically
More than 50% of the stars in the universe are
binary stars
Used to determine stellar mass

Stellar mass
•

Determined using binary stars – the center of
mass is closest to the most massive star

Binary stars
orbit each
other around
their common
center of
mass
Figure 24.4

24.1 Properties of stars (continued)
 Binary
•

stars and stellar mass

Stellar mass
•

Mass of most stars is between one-tenth and
fifty times the mass of the Sun

24.1 Hertzsprung-Russell
diagram
 Shows
•
•

the relation between stellar

Brightness (absolute magnitude) and
Temperature

 Diagram

is made by plotting (graphing)
each star's
•
•

Luminosity (brightness) and
Temperature

24.1 Hertzsprung-Russell
diagram (continued)
 Parts
•

Main-sequence stars
•

•
•

•

of an H-R diagram

90% of all stars
Band through the center of the H-R diagram
Sun is in the main-sequence

Giants (or red giants)
•
•
•

Very luminous
Large
Upper-right on the H-R diagram

24.1 Hertzsprung-Russell
diagram (continued)
 Parts
•

Giants (or red giants)
•

•

•

of an H-R diagram

Very large giants are called supergiants
Only a few percent of all stars

White dwarfs
•
•

•
•
•

Fainter than main-sequence stars
Small (approximate the size of Earth)
Lower-central area on the H-R diagram
Not all are white in color
Perhaps 10% of all stars

Idealized HertzsprungRussell diagram

Figure 24.5

Quiz Break

24.2 Variable stars
 Stars

that fluctuate in brightness
 Types of variable stars
•

Pulsating variables
•
•

•

Fluctuate regularly in brightness
Expand and contract in size

Eruptive variables
•
•
•

Explosive event
Sudden brightening
Called a nova

24.2 Interstellar matter
 Between

the stars is "the vacuum of

space"
 Nebula
•
•

Cloud of dust and gases
Two major types of nebulae
•

Bright nebula
• Glows if it close to a very hot star
• Two types of bright nebulae
• Emission nebula
• Reflection nebula

The Orion Nebula is a wellknown emission nebula

Figure 24.8

A faint blue reflection nebula in
the Pleiades star cluster

Figure 24.9

24.2 Interstellar matter (continued)
 Nebula
•

Two major types of nebulae
•

Dark nebula
• Not close to any bright star
• Appear dark
• Contains the material that forms stars and
planets

24.2 Stellar evolution
 Stars

exist because of gravity
 Two opposing forces in a star are
•
•

Gravity – contracts
Thermal nuclear energy – expands

 Stages
•

Birth
•

•
•
•
•

In dark, cool, interstellar clouds
Gravity contracts the cloud
Temperature rises
Radiates long-wavelength (red) light
Becomes a protostar

24.2 Stellar evolution (continued)
 Stages
•

Protostar
•
•
•

•
•
•
•

Gravitational contraction of gaseous cloud
continues
Core reaches 10 million K
Hydrogen nuclei fuse
• Become helium nuclei
• Process is called hydrogen burning
Energy is released
Outward pressure increases
Outward pressure balanced by gravity pulling in
Star becomes a stable main-sequence star

24.2 Stellar evolution (continued)
 Stages
•

Main-sequence stage
•

Stars age at different rates
• Massive stars use fuel faster and exist for
only a few million years
• Small stars use fuel slowly and exist for
perhaps hundreds of billions of years

•

90% of a star's life is in the main-sequence

24.2 Stellar evolution (continued)
 Stages
•

Red giant stage
•
•

•
•
•

Hydrogen burning migrates outward
Star's outer envelope expands
• Surface cools
• Surface becomes red
Core is collapsing as helium is converted to
carbon
Eventually all nuclear fuel is used
Gravity squeezes the star

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Low-mass star
• 0.5 solar mass
• Red giant collapses
• Becomes a white dwarf

24.2 Evolutionary stages of
low mass stars

Figure 24.12 A

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Medium-mass star
• Between 0.5 and 3 solar masses
• Red giant collapses
• Planetary nebula forms
• Becomes a white dwarf

24.2 Evolutionary stages of
medium mass stars

Figure 24.12 B

H-R diagram showing
stellar evolution

Figure 24.11

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Massive star
• Over 3 solar masses
• Short life span
• Terminates in a brilliant explosion called
a supernova
• Interior condenses
• May produce a hot, dense object that is
either a neutron star or a black hole

24.2 Evolutionary stages of
massive stars

Figure 24.12 C

24.2 Stellar remnants
 White
•
•

Small (some no larger than Earth)
Dense
•
•
•

•
•

dwarf

Can be more massive than the Sun
Spoonful weighs several tons
Atoms take up less space
• Electrons displaced inward
• Called degenerate matter

Hot surface
Cools to become a black dwarf

24.2 Stellar remnants (continued)
 Neutron
•

Forms from a more massive star
•
•

•
•

star

Star has more gravity
Squeezes itself smaller

Remnant of a supernova
Gravitational force collapses atoms
•
•

Electrons combine with protons to produce
neutrons
Small size

24.2 Stellar remnants (continued)
 Neutron
•

Pea size sample
•
•

•
•

star

Weighs 100 million tons
Same density as an atomic nucleus

Strong magnetic field
First one discovered in early 1970s
•
•

Pulsar (pulsating radio source)
Found in the Crab nebula (remnant of an A.D.
1054 supernova)

Crab Nebula in the
constellation Taurus

Figure 24.14

24.2 Stellar remnants (continued)
 Black
•
•

•

More dense than a neutron star
Intense surface gravity lets no light escape
As matter is pulled into it
•
•

•

hole

Becomes very hot
Emits x-rays

Likely candidate is Cygnus X-1, a strong xray source

Quiz Break

24.3 Galaxies
 Milky
•

Way galaxy

Structure
•
•

•
•

Determined by using radio telescopes
Large spiral galaxy
• About 100,000 light-years wide
• Thickness at the galactic nucleus is about
10,000 light-years
Three spiral arms of stars
Sun is 30,000 light-years from the center

Face-on view of the
Milk Way Galaxy

Figure 24.18 A

Edge-on view of the
Milk Way Galaxy

Figure 24.18 B

24.3 Galaxies (continued)
 Milky
•

Rotation
•
•
•

•

Way galaxy

Around the galactic nucleus
Outermost stars move the slowest
Sun rotates around the galactic nucleus once
about every 200 million years

Halo surrounds the galactic disk
•
•
•

Spherical
Very tenuous gas
Numerous globular clusters

24.3 Galaxies (continued)
 Other
•
•

galaxies

Existence was first proposed in mid-1700s
by Immanuel Kant
Four basic types of galaxies
•

Spiral galaxy
• Arms extending from nucleus
• About 30% of all galaxies
• Large diameter of 20,000 to 125,000 light
years
• Contains both young and old stars
• e.g., Milky Way

Great Galaxy, a spiral galaxy, in
the constellation Andromeda

Figure 24.20

24.3 Galaxies (continued)
 Other
•

galaxies

Four basic types of galaxies
•

•

Barred spiral galaxy
• Stars arranged in the shape of a bar
• Generally quite large
• About 10% of all galaxies
Elliptical galaxy
• Ellipsoidal shape
• About 60% of all galaxies
• Most are smaller than spiral galaxies;
however, they are also the largest known
galaxies

A barred spiral galaxy

Figure 24.22

24.3 Galaxies (continued)
 Other
•

galaxies

Four basic types of galaxies
•

Irregular galaxy
• Lacks symmetry
• About 10% of all galaxies
• Contains mostly young stars
• e.g., Magellanic Clouds

24.3 Galaxies (continued)
 Galactic
•
•
•

Group of galaxies
Some contain thousands of galaxies
Local Group
•
•

•

cluster

Our own group of galaxies
Contains at least 28 galaxies

Supercluster
•
•

Huge swarm of galaxies
May be the largest entity in the universe

Quiz Break

24.4 Red shifts
 Doppler
•

effect

Change in the wavelength of light emitted
by an object due to its motion
•

•

Movement away stretches the wavelength
• Longer wavelength
• Light appears redder
Movement toward “squeezes” the wavelength
• Shorter wavelength
• Light shifted toward the blue

24.4 Red shifts (continued)
 Doppler
•

effect

Amount of the Doppler shift indicates the
rate of movement
•
•

Large Doppler shift indicates a high velocity
Small Doppler shift indicates a lower velocity

 Expanding
•

universe

Most galaxies exhibit a red Doppler shift
•

Moving away

Raisin bread analogy of an
expanding universe

Figure 24.24

24.4 Red shifts (continued)
 Expanding
•

universe

Most galaxies exhibit a red Doppler shift
•

•
•
•

Far galaxies
• Exhibit the greatest shift
• Greater velocity
Discovered in 1929 by Edwin Hubble
Hubble's Law – the recessional speed of
galaxies is proportional to their distance
Accounts for red shifts

24.4 Big Bang theory
 Accounts

for galaxies moving away

from us
 Universe was once confined to a "ball"
that was
•
•

•

Supermassive
Dense
Hot

24.4 Big Bang theory (continued)
 Big

Bang marks the inception of the
universe
•
•

Occurred about 15 billion years ago
All matter and space was created

 Matter

is moving outward
 Fate of the universe
•

Two possibilities
•
•

Universe will last forever
Outward expansion sill stop and gravitational;
contraction will follow

24.4 Big Bang theory (continued)
 Fate
•

of the universe

Final fate depends on the average density
of the universe
•
•

If the density is more than the critical density,
then the universe would contract
Current estimates point to less then the critical
density and predict an ever-expanding, or
open, universe

Chapter 24Test Guidance
You will be responsible on the test for answering 3 of the following 6
questions.
1.

2.

3.
4.
5.
6.

What causes the difference between a star’s apparent
magnitude and it absolute magnitude.
List and explain the three factors that control the apparent
brightness of a star as seen from Earth.
Describe how binary stars are used to determine stellar mass.
List and describe the four basic types of galaxies.
What is Hubble’s Law, please explain in detail.
Briefly describe the Big Bang Theory (not the TV show).

End of Chapter 24


Slide 15

Lecture Outlines
PowerPoint

Chapter 24
Earth Science 11e
Tarbuck/Lutgens
Modified for educational
purposes only
By S. Koziol 12-8-2010

© 2006 Pearson Prentice Hall

Earth Science, 11e
Beyond Our
Solar System
Chapter 24

24.1 Properties of stars
 Distance
•
•

Measuring a star's distance can be very
difficult
Stellar parallax
•
•
•

•
•

Used for measuring distance to a star
Apparent shift in a star's position due to the
orbital motion of Earth
Measured as an angle
Near stars have the largest parallax
Largest parallax is less than one second of arc

24. 1 Properties of stars
(continued)

 Distance
•
•

Distances to the stars are very large
Units of measurement
•
•

•

Kilometers or astronomical units are too
cumbersome to use
Light-year is used most often
• Distance that light travels in 1 year
• One light-year is 9.5 trillion km (5.8 trillion
miles)

Other methods for measuring distance are
also used

24. 1 Properties of stars
(continued)

 Stellar
•

Controlled by three factors
•

•
•

•

brightness

Size
Temperature
Distance

Magnitude
•

Measure of a star's brightness

24.1 Properties of stars
(continued)

 Stellar
•

brightness

Magnitude
•

Two types of measurement
• Apparent magnitude
• Brightness when a star is viewed from
Earth
• Decreases with distance
• Numbers are used to designate
magnitudes - dim stars have large
numbers and negative numbers are also
used

24.1 Properties of stars
(continued)

 Stellar
•

brightness

Magnitude
•

Two types of measurement
• Absolute magnitude
• "True" or intrinsic brightness of a star
• Brightness at a standard distance of
32.6 light-years
• Most stars' absolute magnitudes are
between -5 and +15

24.1 Properties of stars
(continued)

 Color
•

Hot star
•

•
•

•

and temperature

Temperature above 30,000 K
Emits short-wavelength light
Appears blue

Cool star
•
•
•

Temperature less than 3000 K
Emits longer-wavelength light
Appears red

24.1 Properties of stars
(continued)

 Color
•

and temperature

Between 5000 and 6000 K
•
•

Stars appear yellow
e.g., Sun

 Binary
•

stars and stellar mass

Binary stars
•

Two stars orbiting one another
• Stars are held together by mutual
gravitation
• Both orbit around a common center of mass

24.1 Properties of stars (continued)
 Binary
•

Binary stars
•

•
•

•

stars and stellar mass

Visual binaries are resolved telescopically
More than 50% of the stars in the universe are
binary stars
Used to determine stellar mass

Stellar mass
•

Determined using binary stars – the center of
mass is closest to the most massive star

Binary stars
orbit each
other around
their common
center of
mass
Figure 24.4

24.1 Properties of stars (continued)
 Binary
•

stars and stellar mass

Stellar mass
•

Mass of most stars is between one-tenth and
fifty times the mass of the Sun

24.1 Hertzsprung-Russell
diagram
 Shows
•
•

the relation between stellar

Brightness (absolute magnitude) and
Temperature

 Diagram

is made by plotting (graphing)
each star's
•
•

Luminosity (brightness) and
Temperature

24.1 Hertzsprung-Russell
diagram (continued)
 Parts
•

Main-sequence stars
•

•
•

•

of an H-R diagram

90% of all stars
Band through the center of the H-R diagram
Sun is in the main-sequence

Giants (or red giants)
•
•
•

Very luminous
Large
Upper-right on the H-R diagram

24.1 Hertzsprung-Russell
diagram (continued)
 Parts
•

Giants (or red giants)
•

•

•

of an H-R diagram

Very large giants are called supergiants
Only a few percent of all stars

White dwarfs
•
•

•
•
•

Fainter than main-sequence stars
Small (approximate the size of Earth)
Lower-central area on the H-R diagram
Not all are white in color
Perhaps 10% of all stars

Idealized HertzsprungRussell diagram

Figure 24.5

Quiz Break

24.2 Variable stars
 Stars

that fluctuate in brightness
 Types of variable stars
•

Pulsating variables
•
•

•

Fluctuate regularly in brightness
Expand and contract in size

Eruptive variables
•
•
•

Explosive event
Sudden brightening
Called a nova

24.2 Interstellar matter
 Between

the stars is "the vacuum of

space"
 Nebula
•
•

Cloud of dust and gases
Two major types of nebulae
•

Bright nebula
• Glows if it close to a very hot star
• Two types of bright nebulae
• Emission nebula
• Reflection nebula

The Orion Nebula is a wellknown emission nebula

Figure 24.8

A faint blue reflection nebula in
the Pleiades star cluster

Figure 24.9

24.2 Interstellar matter (continued)
 Nebula
•

Two major types of nebulae
•

Dark nebula
• Not close to any bright star
• Appear dark
• Contains the material that forms stars and
planets

24.2 Stellar evolution
 Stars

exist because of gravity
 Two opposing forces in a star are
•
•

Gravity – contracts
Thermal nuclear energy – expands

 Stages
•

Birth
•

•
•
•
•

In dark, cool, interstellar clouds
Gravity contracts the cloud
Temperature rises
Radiates long-wavelength (red) light
Becomes a protostar

24.2 Stellar evolution (continued)
 Stages
•

Protostar
•
•
•

•
•
•
•

Gravitational contraction of gaseous cloud
continues
Core reaches 10 million K
Hydrogen nuclei fuse
• Become helium nuclei
• Process is called hydrogen burning
Energy is released
Outward pressure increases
Outward pressure balanced by gravity pulling in
Star becomes a stable main-sequence star

24.2 Stellar evolution (continued)
 Stages
•

Main-sequence stage
•

Stars age at different rates
• Massive stars use fuel faster and exist for
only a few million years
• Small stars use fuel slowly and exist for
perhaps hundreds of billions of years

•

90% of a star's life is in the main-sequence

24.2 Stellar evolution (continued)
 Stages
•

Red giant stage
•
•

•
•
•

Hydrogen burning migrates outward
Star's outer envelope expands
• Surface cools
• Surface becomes red
Core is collapsing as helium is converted to
carbon
Eventually all nuclear fuel is used
Gravity squeezes the star

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Low-mass star
• 0.5 solar mass
• Red giant collapses
• Becomes a white dwarf

24.2 Evolutionary stages of
low mass stars

Figure 24.12 A

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Medium-mass star
• Between 0.5 and 3 solar masses
• Red giant collapses
• Planetary nebula forms
• Becomes a white dwarf

24.2 Evolutionary stages of
medium mass stars

Figure 24.12 B

H-R diagram showing
stellar evolution

Figure 24.11

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Massive star
• Over 3 solar masses
• Short life span
• Terminates in a brilliant explosion called
a supernova
• Interior condenses
• May produce a hot, dense object that is
either a neutron star or a black hole

24.2 Evolutionary stages of
massive stars

Figure 24.12 C

24.2 Stellar remnants
 White
•
•

Small (some no larger than Earth)
Dense
•
•
•

•
•

dwarf

Can be more massive than the Sun
Spoonful weighs several tons
Atoms take up less space
• Electrons displaced inward
• Called degenerate matter

Hot surface
Cools to become a black dwarf

24.2 Stellar remnants (continued)
 Neutron
•

Forms from a more massive star
•
•

•
•

star

Star has more gravity
Squeezes itself smaller

Remnant of a supernova
Gravitational force collapses atoms
•
•

Electrons combine with protons to produce
neutrons
Small size

24.2 Stellar remnants (continued)
 Neutron
•

Pea size sample
•
•

•
•

star

Weighs 100 million tons
Same density as an atomic nucleus

Strong magnetic field
First one discovered in early 1970s
•
•

Pulsar (pulsating radio source)
Found in the Crab nebula (remnant of an A.D.
1054 supernova)

Crab Nebula in the
constellation Taurus

Figure 24.14

24.2 Stellar remnants (continued)
 Black
•
•

•

More dense than a neutron star
Intense surface gravity lets no light escape
As matter is pulled into it
•
•

•

hole

Becomes very hot
Emits x-rays

Likely candidate is Cygnus X-1, a strong xray source

Quiz Break

24.3 Galaxies
 Milky
•

Way galaxy

Structure
•
•

•
•

Determined by using radio telescopes
Large spiral galaxy
• About 100,000 light-years wide
• Thickness at the galactic nucleus is about
10,000 light-years
Three spiral arms of stars
Sun is 30,000 light-years from the center

Face-on view of the
Milk Way Galaxy

Figure 24.18 A

Edge-on view of the
Milk Way Galaxy

Figure 24.18 B

24.3 Galaxies (continued)
 Milky
•

Rotation
•
•
•

•

Way galaxy

Around the galactic nucleus
Outermost stars move the slowest
Sun rotates around the galactic nucleus once
about every 200 million years

Halo surrounds the galactic disk
•
•
•

Spherical
Very tenuous gas
Numerous globular clusters

24.3 Galaxies (continued)
 Other
•
•

galaxies

Existence was first proposed in mid-1700s
by Immanuel Kant
Four basic types of galaxies
•

Spiral galaxy
• Arms extending from nucleus
• About 30% of all galaxies
• Large diameter of 20,000 to 125,000 light
years
• Contains both young and old stars
• e.g., Milky Way

Great Galaxy, a spiral galaxy, in
the constellation Andromeda

Figure 24.20

24.3 Galaxies (continued)
 Other
•

galaxies

Four basic types of galaxies
•

•

Barred spiral galaxy
• Stars arranged in the shape of a bar
• Generally quite large
• About 10% of all galaxies
Elliptical galaxy
• Ellipsoidal shape
• About 60% of all galaxies
• Most are smaller than spiral galaxies;
however, they are also the largest known
galaxies

A barred spiral galaxy

Figure 24.22

24.3 Galaxies (continued)
 Other
•

galaxies

Four basic types of galaxies
•

Irregular galaxy
• Lacks symmetry
• About 10% of all galaxies
• Contains mostly young stars
• e.g., Magellanic Clouds

24.3 Galaxies (continued)
 Galactic
•
•
•

Group of galaxies
Some contain thousands of galaxies
Local Group
•
•

•

cluster

Our own group of galaxies
Contains at least 28 galaxies

Supercluster
•
•

Huge swarm of galaxies
May be the largest entity in the universe

Quiz Break

24.4 Red shifts
 Doppler
•

effect

Change in the wavelength of light emitted
by an object due to its motion
•

•

Movement away stretches the wavelength
• Longer wavelength
• Light appears redder
Movement toward “squeezes” the wavelength
• Shorter wavelength
• Light shifted toward the blue

24.4 Red shifts (continued)
 Doppler
•

effect

Amount of the Doppler shift indicates the
rate of movement
•
•

Large Doppler shift indicates a high velocity
Small Doppler shift indicates a lower velocity

 Expanding
•

universe

Most galaxies exhibit a red Doppler shift
•

Moving away

Raisin bread analogy of an
expanding universe

Figure 24.24

24.4 Red shifts (continued)
 Expanding
•

universe

Most galaxies exhibit a red Doppler shift
•

•
•
•

Far galaxies
• Exhibit the greatest shift
• Greater velocity
Discovered in 1929 by Edwin Hubble
Hubble's Law – the recessional speed of
galaxies is proportional to their distance
Accounts for red shifts

24.4 Big Bang theory
 Accounts

for galaxies moving away

from us
 Universe was once confined to a "ball"
that was
•
•

•

Supermassive
Dense
Hot

24.4 Big Bang theory (continued)
 Big

Bang marks the inception of the
universe
•
•

Occurred about 15 billion years ago
All matter and space was created

 Matter

is moving outward
 Fate of the universe
•

Two possibilities
•
•

Universe will last forever
Outward expansion sill stop and gravitational;
contraction will follow

24.4 Big Bang theory (continued)
 Fate
•

of the universe

Final fate depends on the average density
of the universe
•
•

If the density is more than the critical density,
then the universe would contract
Current estimates point to less then the critical
density and predict an ever-expanding, or
open, universe

Chapter 24Test Guidance
You will be responsible on the test for answering 3 of the following 6
questions.
1.

2.

3.
4.
5.
6.

What causes the difference between a star’s apparent
magnitude and it absolute magnitude.
List and explain the three factors that control the apparent
brightness of a star as seen from Earth.
Describe how binary stars are used to determine stellar mass.
List and describe the four basic types of galaxies.
What is Hubble’s Law, please explain in detail.
Briefly describe the Big Bang Theory (not the TV show).

End of Chapter 24


Slide 16

Lecture Outlines
PowerPoint

Chapter 24
Earth Science 11e
Tarbuck/Lutgens
Modified for educational
purposes only
By S. Koziol 12-8-2010

© 2006 Pearson Prentice Hall

Earth Science, 11e
Beyond Our
Solar System
Chapter 24

24.1 Properties of stars
 Distance
•
•

Measuring a star's distance can be very
difficult
Stellar parallax
•
•
•

•
•

Used for measuring distance to a star
Apparent shift in a star's position due to the
orbital motion of Earth
Measured as an angle
Near stars have the largest parallax
Largest parallax is less than one second of arc

24. 1 Properties of stars
(continued)

 Distance
•
•

Distances to the stars are very large
Units of measurement
•
•

•

Kilometers or astronomical units are too
cumbersome to use
Light-year is used most often
• Distance that light travels in 1 year
• One light-year is 9.5 trillion km (5.8 trillion
miles)

Other methods for measuring distance are
also used

24. 1 Properties of stars
(continued)

 Stellar
•

Controlled by three factors
•

•
•

•

brightness

Size
Temperature
Distance

Magnitude
•

Measure of a star's brightness

24.1 Properties of stars
(continued)

 Stellar
•

brightness

Magnitude
•

Two types of measurement
• Apparent magnitude
• Brightness when a star is viewed from
Earth
• Decreases with distance
• Numbers are used to designate
magnitudes - dim stars have large
numbers and negative numbers are also
used

24.1 Properties of stars
(continued)

 Stellar
•

brightness

Magnitude
•

Two types of measurement
• Absolute magnitude
• "True" or intrinsic brightness of a star
• Brightness at a standard distance of
32.6 light-years
• Most stars' absolute magnitudes are
between -5 and +15

24.1 Properties of stars
(continued)

 Color
•

Hot star
•

•
•

•

and temperature

Temperature above 30,000 K
Emits short-wavelength light
Appears blue

Cool star
•
•
•

Temperature less than 3000 K
Emits longer-wavelength light
Appears red

24.1 Properties of stars
(continued)

 Color
•

and temperature

Between 5000 and 6000 K
•
•

Stars appear yellow
e.g., Sun

 Binary
•

stars and stellar mass

Binary stars
•

Two stars orbiting one another
• Stars are held together by mutual
gravitation
• Both orbit around a common center of mass

24.1 Properties of stars (continued)
 Binary
•

Binary stars
•

•
•

•

stars and stellar mass

Visual binaries are resolved telescopically
More than 50% of the stars in the universe are
binary stars
Used to determine stellar mass

Stellar mass
•

Determined using binary stars – the center of
mass is closest to the most massive star

Binary stars
orbit each
other around
their common
center of
mass
Figure 24.4

24.1 Properties of stars (continued)
 Binary
•

stars and stellar mass

Stellar mass
•

Mass of most stars is between one-tenth and
fifty times the mass of the Sun

24.1 Hertzsprung-Russell
diagram
 Shows
•
•

the relation between stellar

Brightness (absolute magnitude) and
Temperature

 Diagram

is made by plotting (graphing)
each star's
•
•

Luminosity (brightness) and
Temperature

24.1 Hertzsprung-Russell
diagram (continued)
 Parts
•

Main-sequence stars
•

•
•

•

of an H-R diagram

90% of all stars
Band through the center of the H-R diagram
Sun is in the main-sequence

Giants (or red giants)
•
•
•

Very luminous
Large
Upper-right on the H-R diagram

24.1 Hertzsprung-Russell
diagram (continued)
 Parts
•

Giants (or red giants)
•

•

•

of an H-R diagram

Very large giants are called supergiants
Only a few percent of all stars

White dwarfs
•
•

•
•
•

Fainter than main-sequence stars
Small (approximate the size of Earth)
Lower-central area on the H-R diagram
Not all are white in color
Perhaps 10% of all stars

Idealized HertzsprungRussell diagram

Figure 24.5

Quiz Break

24.2 Variable stars
 Stars

that fluctuate in brightness
 Types of variable stars
•

Pulsating variables
•
•

•

Fluctuate regularly in brightness
Expand and contract in size

Eruptive variables
•
•
•

Explosive event
Sudden brightening
Called a nova

24.2 Interstellar matter
 Between

the stars is "the vacuum of

space"
 Nebula
•
•

Cloud of dust and gases
Two major types of nebulae
•

Bright nebula
• Glows if it close to a very hot star
• Two types of bright nebulae
• Emission nebula
• Reflection nebula

The Orion Nebula is a wellknown emission nebula

Figure 24.8

A faint blue reflection nebula in
the Pleiades star cluster

Figure 24.9

24.2 Interstellar matter (continued)
 Nebula
•

Two major types of nebulae
•

Dark nebula
• Not close to any bright star
• Appear dark
• Contains the material that forms stars and
planets

24.2 Stellar evolution
 Stars

exist because of gravity
 Two opposing forces in a star are
•
•

Gravity – contracts
Thermal nuclear energy – expands

 Stages
•

Birth
•

•
•
•
•

In dark, cool, interstellar clouds
Gravity contracts the cloud
Temperature rises
Radiates long-wavelength (red) light
Becomes a protostar

24.2 Stellar evolution (continued)
 Stages
•

Protostar
•
•
•

•
•
•
•

Gravitational contraction of gaseous cloud
continues
Core reaches 10 million K
Hydrogen nuclei fuse
• Become helium nuclei
• Process is called hydrogen burning
Energy is released
Outward pressure increases
Outward pressure balanced by gravity pulling in
Star becomes a stable main-sequence star

24.2 Stellar evolution (continued)
 Stages
•

Main-sequence stage
•

Stars age at different rates
• Massive stars use fuel faster and exist for
only a few million years
• Small stars use fuel slowly and exist for
perhaps hundreds of billions of years

•

90% of a star's life is in the main-sequence

24.2 Stellar evolution (continued)
 Stages
•

Red giant stage
•
•

•
•
•

Hydrogen burning migrates outward
Star's outer envelope expands
• Surface cools
• Surface becomes red
Core is collapsing as helium is converted to
carbon
Eventually all nuclear fuel is used
Gravity squeezes the star

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Low-mass star
• 0.5 solar mass
• Red giant collapses
• Becomes a white dwarf

24.2 Evolutionary stages of
low mass stars

Figure 24.12 A

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Medium-mass star
• Between 0.5 and 3 solar masses
• Red giant collapses
• Planetary nebula forms
• Becomes a white dwarf

24.2 Evolutionary stages of
medium mass stars

Figure 24.12 B

H-R diagram showing
stellar evolution

Figure 24.11

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Massive star
• Over 3 solar masses
• Short life span
• Terminates in a brilliant explosion called
a supernova
• Interior condenses
• May produce a hot, dense object that is
either a neutron star or a black hole

24.2 Evolutionary stages of
massive stars

Figure 24.12 C

24.2 Stellar remnants
 White
•
•

Small (some no larger than Earth)
Dense
•
•
•

•
•

dwarf

Can be more massive than the Sun
Spoonful weighs several tons
Atoms take up less space
• Electrons displaced inward
• Called degenerate matter

Hot surface
Cools to become a black dwarf

24.2 Stellar remnants (continued)
 Neutron
•

Forms from a more massive star
•
•

•
•

star

Star has more gravity
Squeezes itself smaller

Remnant of a supernova
Gravitational force collapses atoms
•
•

Electrons combine with protons to produce
neutrons
Small size

24.2 Stellar remnants (continued)
 Neutron
•

Pea size sample
•
•

•
•

star

Weighs 100 million tons
Same density as an atomic nucleus

Strong magnetic field
First one discovered in early 1970s
•
•

Pulsar (pulsating radio source)
Found in the Crab nebula (remnant of an A.D.
1054 supernova)

Crab Nebula in the
constellation Taurus

Figure 24.14

24.2 Stellar remnants (continued)
 Black
•
•

•

More dense than a neutron star
Intense surface gravity lets no light escape
As matter is pulled into it
•
•

•

hole

Becomes very hot
Emits x-rays

Likely candidate is Cygnus X-1, a strong xray source

Quiz Break

24.3 Galaxies
 Milky
•

Way galaxy

Structure
•
•

•
•

Determined by using radio telescopes
Large spiral galaxy
• About 100,000 light-years wide
• Thickness at the galactic nucleus is about
10,000 light-years
Three spiral arms of stars
Sun is 30,000 light-years from the center

Face-on view of the
Milk Way Galaxy

Figure 24.18 A

Edge-on view of the
Milk Way Galaxy

Figure 24.18 B

24.3 Galaxies (continued)
 Milky
•

Rotation
•
•
•

•

Way galaxy

Around the galactic nucleus
Outermost stars move the slowest
Sun rotates around the galactic nucleus once
about every 200 million years

Halo surrounds the galactic disk
•
•
•

Spherical
Very tenuous gas
Numerous globular clusters

24.3 Galaxies (continued)
 Other
•
•

galaxies

Existence was first proposed in mid-1700s
by Immanuel Kant
Four basic types of galaxies
•

Spiral galaxy
• Arms extending from nucleus
• About 30% of all galaxies
• Large diameter of 20,000 to 125,000 light
years
• Contains both young and old stars
• e.g., Milky Way

Great Galaxy, a spiral galaxy, in
the constellation Andromeda

Figure 24.20

24.3 Galaxies (continued)
 Other
•

galaxies

Four basic types of galaxies
•

•

Barred spiral galaxy
• Stars arranged in the shape of a bar
• Generally quite large
• About 10% of all galaxies
Elliptical galaxy
• Ellipsoidal shape
• About 60% of all galaxies
• Most are smaller than spiral galaxies;
however, they are also the largest known
galaxies

A barred spiral galaxy

Figure 24.22

24.3 Galaxies (continued)
 Other
•

galaxies

Four basic types of galaxies
•

Irregular galaxy
• Lacks symmetry
• About 10% of all galaxies
• Contains mostly young stars
• e.g., Magellanic Clouds

24.3 Galaxies (continued)
 Galactic
•
•
•

Group of galaxies
Some contain thousands of galaxies
Local Group
•
•

•

cluster

Our own group of galaxies
Contains at least 28 galaxies

Supercluster
•
•

Huge swarm of galaxies
May be the largest entity in the universe

Quiz Break

24.4 Red shifts
 Doppler
•

effect

Change in the wavelength of light emitted
by an object due to its motion
•

•

Movement away stretches the wavelength
• Longer wavelength
• Light appears redder
Movement toward “squeezes” the wavelength
• Shorter wavelength
• Light shifted toward the blue

24.4 Red shifts (continued)
 Doppler
•

effect

Amount of the Doppler shift indicates the
rate of movement
•
•

Large Doppler shift indicates a high velocity
Small Doppler shift indicates a lower velocity

 Expanding
•

universe

Most galaxies exhibit a red Doppler shift
•

Moving away

Raisin bread analogy of an
expanding universe

Figure 24.24

24.4 Red shifts (continued)
 Expanding
•

universe

Most galaxies exhibit a red Doppler shift
•

•
•
•

Far galaxies
• Exhibit the greatest shift
• Greater velocity
Discovered in 1929 by Edwin Hubble
Hubble's Law – the recessional speed of
galaxies is proportional to their distance
Accounts for red shifts

24.4 Big Bang theory
 Accounts

for galaxies moving away

from us
 Universe was once confined to a "ball"
that was
•
•

•

Supermassive
Dense
Hot

24.4 Big Bang theory (continued)
 Big

Bang marks the inception of the
universe
•
•

Occurred about 15 billion years ago
All matter and space was created

 Matter

is moving outward
 Fate of the universe
•

Two possibilities
•
•

Universe will last forever
Outward expansion sill stop and gravitational;
contraction will follow

24.4 Big Bang theory (continued)
 Fate
•

of the universe

Final fate depends on the average density
of the universe
•
•

If the density is more than the critical density,
then the universe would contract
Current estimates point to less then the critical
density and predict an ever-expanding, or
open, universe

Chapter 24Test Guidance
You will be responsible on the test for answering 3 of the following 6
questions.
1.

2.

3.
4.
5.
6.

What causes the difference between a star’s apparent
magnitude and it absolute magnitude.
List and explain the three factors that control the apparent
brightness of a star as seen from Earth.
Describe how binary stars are used to determine stellar mass.
List and describe the four basic types of galaxies.
What is Hubble’s Law, please explain in detail.
Briefly describe the Big Bang Theory (not the TV show).

End of Chapter 24


Slide 17

Lecture Outlines
PowerPoint

Chapter 24
Earth Science 11e
Tarbuck/Lutgens
Modified for educational
purposes only
By S. Koziol 12-8-2010

© 2006 Pearson Prentice Hall

Earth Science, 11e
Beyond Our
Solar System
Chapter 24

24.1 Properties of stars
 Distance
•
•

Measuring a star's distance can be very
difficult
Stellar parallax
•
•
•

•
•

Used for measuring distance to a star
Apparent shift in a star's position due to the
orbital motion of Earth
Measured as an angle
Near stars have the largest parallax
Largest parallax is less than one second of arc

24. 1 Properties of stars
(continued)

 Distance
•
•

Distances to the stars are very large
Units of measurement
•
•

•

Kilometers or astronomical units are too
cumbersome to use
Light-year is used most often
• Distance that light travels in 1 year
• One light-year is 9.5 trillion km (5.8 trillion
miles)

Other methods for measuring distance are
also used

24. 1 Properties of stars
(continued)

 Stellar
•

Controlled by three factors
•

•
•

•

brightness

Size
Temperature
Distance

Magnitude
•

Measure of a star's brightness

24.1 Properties of stars
(continued)

 Stellar
•

brightness

Magnitude
•

Two types of measurement
• Apparent magnitude
• Brightness when a star is viewed from
Earth
• Decreases with distance
• Numbers are used to designate
magnitudes - dim stars have large
numbers and negative numbers are also
used

24.1 Properties of stars
(continued)

 Stellar
•

brightness

Magnitude
•

Two types of measurement
• Absolute magnitude
• "True" or intrinsic brightness of a star
• Brightness at a standard distance of
32.6 light-years
• Most stars' absolute magnitudes are
between -5 and +15

24.1 Properties of stars
(continued)

 Color
•

Hot star
•

•
•

•

and temperature

Temperature above 30,000 K
Emits short-wavelength light
Appears blue

Cool star
•
•
•

Temperature less than 3000 K
Emits longer-wavelength light
Appears red

24.1 Properties of stars
(continued)

 Color
•

and temperature

Between 5000 and 6000 K
•
•

Stars appear yellow
e.g., Sun

 Binary
•

stars and stellar mass

Binary stars
•

Two stars orbiting one another
• Stars are held together by mutual
gravitation
• Both orbit around a common center of mass

24.1 Properties of stars (continued)
 Binary
•

Binary stars
•

•
•

•

stars and stellar mass

Visual binaries are resolved telescopically
More than 50% of the stars in the universe are
binary stars
Used to determine stellar mass

Stellar mass
•

Determined using binary stars – the center of
mass is closest to the most massive star

Binary stars
orbit each
other around
their common
center of
mass
Figure 24.4

24.1 Properties of stars (continued)
 Binary
•

stars and stellar mass

Stellar mass
•

Mass of most stars is between one-tenth and
fifty times the mass of the Sun

24.1 Hertzsprung-Russell
diagram
 Shows
•
•

the relation between stellar

Brightness (absolute magnitude) and
Temperature

 Diagram

is made by plotting (graphing)
each star's
•
•

Luminosity (brightness) and
Temperature

24.1 Hertzsprung-Russell
diagram (continued)
 Parts
•

Main-sequence stars
•

•
•

•

of an H-R diagram

90% of all stars
Band through the center of the H-R diagram
Sun is in the main-sequence

Giants (or red giants)
•
•
•

Very luminous
Large
Upper-right on the H-R diagram

24.1 Hertzsprung-Russell
diagram (continued)
 Parts
•

Giants (or red giants)
•

•

•

of an H-R diagram

Very large giants are called supergiants
Only a few percent of all stars

White dwarfs
•
•

•
•
•

Fainter than main-sequence stars
Small (approximate the size of Earth)
Lower-central area on the H-R diagram
Not all are white in color
Perhaps 10% of all stars

Idealized HertzsprungRussell diagram

Figure 24.5

Quiz Break

24.2 Variable stars
 Stars

that fluctuate in brightness
 Types of variable stars
•

Pulsating variables
•
•

•

Fluctuate regularly in brightness
Expand and contract in size

Eruptive variables
•
•
•

Explosive event
Sudden brightening
Called a nova

24.2 Interstellar matter
 Between

the stars is "the vacuum of

space"
 Nebula
•
•

Cloud of dust and gases
Two major types of nebulae
•

Bright nebula
• Glows if it close to a very hot star
• Two types of bright nebulae
• Emission nebula
• Reflection nebula

The Orion Nebula is a wellknown emission nebula

Figure 24.8

A faint blue reflection nebula in
the Pleiades star cluster

Figure 24.9

24.2 Interstellar matter (continued)
 Nebula
•

Two major types of nebulae
•

Dark nebula
• Not close to any bright star
• Appear dark
• Contains the material that forms stars and
planets

24.2 Stellar evolution
 Stars

exist because of gravity
 Two opposing forces in a star are
•
•

Gravity – contracts
Thermal nuclear energy – expands

 Stages
•

Birth
•

•
•
•
•

In dark, cool, interstellar clouds
Gravity contracts the cloud
Temperature rises
Radiates long-wavelength (red) light
Becomes a protostar

24.2 Stellar evolution (continued)
 Stages
•

Protostar
•
•
•

•
•
•
•

Gravitational contraction of gaseous cloud
continues
Core reaches 10 million K
Hydrogen nuclei fuse
• Become helium nuclei
• Process is called hydrogen burning
Energy is released
Outward pressure increases
Outward pressure balanced by gravity pulling in
Star becomes a stable main-sequence star

24.2 Stellar evolution (continued)
 Stages
•

Main-sequence stage
•

Stars age at different rates
• Massive stars use fuel faster and exist for
only a few million years
• Small stars use fuel slowly and exist for
perhaps hundreds of billions of years

•

90% of a star's life is in the main-sequence

24.2 Stellar evolution (continued)
 Stages
•

Red giant stage
•
•

•
•
•

Hydrogen burning migrates outward
Star's outer envelope expands
• Surface cools
• Surface becomes red
Core is collapsing as helium is converted to
carbon
Eventually all nuclear fuel is used
Gravity squeezes the star

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Low-mass star
• 0.5 solar mass
• Red giant collapses
• Becomes a white dwarf

24.2 Evolutionary stages of
low mass stars

Figure 24.12 A

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Medium-mass star
• Between 0.5 and 3 solar masses
• Red giant collapses
• Planetary nebula forms
• Becomes a white dwarf

24.2 Evolutionary stages of
medium mass stars

Figure 24.12 B

H-R diagram showing
stellar evolution

Figure 24.11

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Massive star
• Over 3 solar masses
• Short life span
• Terminates in a brilliant explosion called
a supernova
• Interior condenses
• May produce a hot, dense object that is
either a neutron star or a black hole

24.2 Evolutionary stages of
massive stars

Figure 24.12 C

24.2 Stellar remnants
 White
•
•

Small (some no larger than Earth)
Dense
•
•
•

•
•

dwarf

Can be more massive than the Sun
Spoonful weighs several tons
Atoms take up less space
• Electrons displaced inward
• Called degenerate matter

Hot surface
Cools to become a black dwarf

24.2 Stellar remnants (continued)
 Neutron
•

Forms from a more massive star
•
•

•
•

star

Star has more gravity
Squeezes itself smaller

Remnant of a supernova
Gravitational force collapses atoms
•
•

Electrons combine with protons to produce
neutrons
Small size

24.2 Stellar remnants (continued)
 Neutron
•

Pea size sample
•
•

•
•

star

Weighs 100 million tons
Same density as an atomic nucleus

Strong magnetic field
First one discovered in early 1970s
•
•

Pulsar (pulsating radio source)
Found in the Crab nebula (remnant of an A.D.
1054 supernova)

Crab Nebula in the
constellation Taurus

Figure 24.14

24.2 Stellar remnants (continued)
 Black
•
•

•

More dense than a neutron star
Intense surface gravity lets no light escape
As matter is pulled into it
•
•

•

hole

Becomes very hot
Emits x-rays

Likely candidate is Cygnus X-1, a strong xray source

Quiz Break

24.3 Galaxies
 Milky
•

Way galaxy

Structure
•
•

•
•

Determined by using radio telescopes
Large spiral galaxy
• About 100,000 light-years wide
• Thickness at the galactic nucleus is about
10,000 light-years
Three spiral arms of stars
Sun is 30,000 light-years from the center

Face-on view of the
Milk Way Galaxy

Figure 24.18 A

Edge-on view of the
Milk Way Galaxy

Figure 24.18 B

24.3 Galaxies (continued)
 Milky
•

Rotation
•
•
•

•

Way galaxy

Around the galactic nucleus
Outermost stars move the slowest
Sun rotates around the galactic nucleus once
about every 200 million years

Halo surrounds the galactic disk
•
•
•

Spherical
Very tenuous gas
Numerous globular clusters

24.3 Galaxies (continued)
 Other
•
•

galaxies

Existence was first proposed in mid-1700s
by Immanuel Kant
Four basic types of galaxies
•

Spiral galaxy
• Arms extending from nucleus
• About 30% of all galaxies
• Large diameter of 20,000 to 125,000 light
years
• Contains both young and old stars
• e.g., Milky Way

Great Galaxy, a spiral galaxy, in
the constellation Andromeda

Figure 24.20

24.3 Galaxies (continued)
 Other
•

galaxies

Four basic types of galaxies
•

•

Barred spiral galaxy
• Stars arranged in the shape of a bar
• Generally quite large
• About 10% of all galaxies
Elliptical galaxy
• Ellipsoidal shape
• About 60% of all galaxies
• Most are smaller than spiral galaxies;
however, they are also the largest known
galaxies

A barred spiral galaxy

Figure 24.22

24.3 Galaxies (continued)
 Other
•

galaxies

Four basic types of galaxies
•

Irregular galaxy
• Lacks symmetry
• About 10% of all galaxies
• Contains mostly young stars
• e.g., Magellanic Clouds

24.3 Galaxies (continued)
 Galactic
•
•
•

Group of galaxies
Some contain thousands of galaxies
Local Group
•
•

•

cluster

Our own group of galaxies
Contains at least 28 galaxies

Supercluster
•
•

Huge swarm of galaxies
May be the largest entity in the universe

Quiz Break

24.4 Red shifts
 Doppler
•

effect

Change in the wavelength of light emitted
by an object due to its motion
•

•

Movement away stretches the wavelength
• Longer wavelength
• Light appears redder
Movement toward “squeezes” the wavelength
• Shorter wavelength
• Light shifted toward the blue

24.4 Red shifts (continued)
 Doppler
•

effect

Amount of the Doppler shift indicates the
rate of movement
•
•

Large Doppler shift indicates a high velocity
Small Doppler shift indicates a lower velocity

 Expanding
•

universe

Most galaxies exhibit a red Doppler shift
•

Moving away

Raisin bread analogy of an
expanding universe

Figure 24.24

24.4 Red shifts (continued)
 Expanding
•

universe

Most galaxies exhibit a red Doppler shift
•

•
•
•

Far galaxies
• Exhibit the greatest shift
• Greater velocity
Discovered in 1929 by Edwin Hubble
Hubble's Law – the recessional speed of
galaxies is proportional to their distance
Accounts for red shifts

24.4 Big Bang theory
 Accounts

for galaxies moving away

from us
 Universe was once confined to a "ball"
that was
•
•

•

Supermassive
Dense
Hot

24.4 Big Bang theory (continued)
 Big

Bang marks the inception of the
universe
•
•

Occurred about 15 billion years ago
All matter and space was created

 Matter

is moving outward
 Fate of the universe
•

Two possibilities
•
•

Universe will last forever
Outward expansion sill stop and gravitational;
contraction will follow

24.4 Big Bang theory (continued)
 Fate
•

of the universe

Final fate depends on the average density
of the universe
•
•

If the density is more than the critical density,
then the universe would contract
Current estimates point to less then the critical
density and predict an ever-expanding, or
open, universe

Chapter 24Test Guidance
You will be responsible on the test for answering 3 of the following 6
questions.
1.

2.

3.
4.
5.
6.

What causes the difference between a star’s apparent
magnitude and it absolute magnitude.
List and explain the three factors that control the apparent
brightness of a star as seen from Earth.
Describe how binary stars are used to determine stellar mass.
List and describe the four basic types of galaxies.
What is Hubble’s Law, please explain in detail.
Briefly describe the Big Bang Theory (not the TV show).

End of Chapter 24


Slide 18

Lecture Outlines
PowerPoint

Chapter 24
Earth Science 11e
Tarbuck/Lutgens
Modified for educational
purposes only
By S. Koziol 12-8-2010

© 2006 Pearson Prentice Hall

Earth Science, 11e
Beyond Our
Solar System
Chapter 24

24.1 Properties of stars
 Distance
•
•

Measuring a star's distance can be very
difficult
Stellar parallax
•
•
•

•
•

Used for measuring distance to a star
Apparent shift in a star's position due to the
orbital motion of Earth
Measured as an angle
Near stars have the largest parallax
Largest parallax is less than one second of arc

24. 1 Properties of stars
(continued)

 Distance
•
•

Distances to the stars are very large
Units of measurement
•
•

•

Kilometers or astronomical units are too
cumbersome to use
Light-year is used most often
• Distance that light travels in 1 year
• One light-year is 9.5 trillion km (5.8 trillion
miles)

Other methods for measuring distance are
also used

24. 1 Properties of stars
(continued)

 Stellar
•

Controlled by three factors
•

•
•

•

brightness

Size
Temperature
Distance

Magnitude
•

Measure of a star's brightness

24.1 Properties of stars
(continued)

 Stellar
•

brightness

Magnitude
•

Two types of measurement
• Apparent magnitude
• Brightness when a star is viewed from
Earth
• Decreases with distance
• Numbers are used to designate
magnitudes - dim stars have large
numbers and negative numbers are also
used

24.1 Properties of stars
(continued)

 Stellar
•

brightness

Magnitude
•

Two types of measurement
• Absolute magnitude
• "True" or intrinsic brightness of a star
• Brightness at a standard distance of
32.6 light-years
• Most stars' absolute magnitudes are
between -5 and +15

24.1 Properties of stars
(continued)

 Color
•

Hot star
•

•
•

•

and temperature

Temperature above 30,000 K
Emits short-wavelength light
Appears blue

Cool star
•
•
•

Temperature less than 3000 K
Emits longer-wavelength light
Appears red

24.1 Properties of stars
(continued)

 Color
•

and temperature

Between 5000 and 6000 K
•
•

Stars appear yellow
e.g., Sun

 Binary
•

stars and stellar mass

Binary stars
•

Two stars orbiting one another
• Stars are held together by mutual
gravitation
• Both orbit around a common center of mass

24.1 Properties of stars (continued)
 Binary
•

Binary stars
•

•
•

•

stars and stellar mass

Visual binaries are resolved telescopically
More than 50% of the stars in the universe are
binary stars
Used to determine stellar mass

Stellar mass
•

Determined using binary stars – the center of
mass is closest to the most massive star

Binary stars
orbit each
other around
their common
center of
mass
Figure 24.4

24.1 Properties of stars (continued)
 Binary
•

stars and stellar mass

Stellar mass
•

Mass of most stars is between one-tenth and
fifty times the mass of the Sun

24.1 Hertzsprung-Russell
diagram
 Shows
•
•

the relation between stellar

Brightness (absolute magnitude) and
Temperature

 Diagram

is made by plotting (graphing)
each star's
•
•

Luminosity (brightness) and
Temperature

24.1 Hertzsprung-Russell
diagram (continued)
 Parts
•

Main-sequence stars
•

•
•

•

of an H-R diagram

90% of all stars
Band through the center of the H-R diagram
Sun is in the main-sequence

Giants (or red giants)
•
•
•

Very luminous
Large
Upper-right on the H-R diagram

24.1 Hertzsprung-Russell
diagram (continued)
 Parts
•

Giants (or red giants)
•

•

•

of an H-R diagram

Very large giants are called supergiants
Only a few percent of all stars

White dwarfs
•
•

•
•
•

Fainter than main-sequence stars
Small (approximate the size of Earth)
Lower-central area on the H-R diagram
Not all are white in color
Perhaps 10% of all stars

Idealized HertzsprungRussell diagram

Figure 24.5

Quiz Break

24.2 Variable stars
 Stars

that fluctuate in brightness
 Types of variable stars
•

Pulsating variables
•
•

•

Fluctuate regularly in brightness
Expand and contract in size

Eruptive variables
•
•
•

Explosive event
Sudden brightening
Called a nova

24.2 Interstellar matter
 Between

the stars is "the vacuum of

space"
 Nebula
•
•

Cloud of dust and gases
Two major types of nebulae
•

Bright nebula
• Glows if it close to a very hot star
• Two types of bright nebulae
• Emission nebula
• Reflection nebula

The Orion Nebula is a wellknown emission nebula

Figure 24.8

A faint blue reflection nebula in
the Pleiades star cluster

Figure 24.9

24.2 Interstellar matter (continued)
 Nebula
•

Two major types of nebulae
•

Dark nebula
• Not close to any bright star
• Appear dark
• Contains the material that forms stars and
planets

24.2 Stellar evolution
 Stars

exist because of gravity
 Two opposing forces in a star are
•
•

Gravity – contracts
Thermal nuclear energy – expands

 Stages
•

Birth
•

•
•
•
•

In dark, cool, interstellar clouds
Gravity contracts the cloud
Temperature rises
Radiates long-wavelength (red) light
Becomes a protostar

24.2 Stellar evolution (continued)
 Stages
•

Protostar
•
•
•

•
•
•
•

Gravitational contraction of gaseous cloud
continues
Core reaches 10 million K
Hydrogen nuclei fuse
• Become helium nuclei
• Process is called hydrogen burning
Energy is released
Outward pressure increases
Outward pressure balanced by gravity pulling in
Star becomes a stable main-sequence star

24.2 Stellar evolution (continued)
 Stages
•

Main-sequence stage
•

Stars age at different rates
• Massive stars use fuel faster and exist for
only a few million years
• Small stars use fuel slowly and exist for
perhaps hundreds of billions of years

•

90% of a star's life is in the main-sequence

24.2 Stellar evolution (continued)
 Stages
•

Red giant stage
•
•

•
•
•

Hydrogen burning migrates outward
Star's outer envelope expands
• Surface cools
• Surface becomes red
Core is collapsing as helium is converted to
carbon
Eventually all nuclear fuel is used
Gravity squeezes the star

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Low-mass star
• 0.5 solar mass
• Red giant collapses
• Becomes a white dwarf

24.2 Evolutionary stages of
low mass stars

Figure 24.12 A

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Medium-mass star
• Between 0.5 and 3 solar masses
• Red giant collapses
• Planetary nebula forms
• Becomes a white dwarf

24.2 Evolutionary stages of
medium mass stars

Figure 24.12 B

H-R diagram showing
stellar evolution

Figure 24.11

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Massive star
• Over 3 solar masses
• Short life span
• Terminates in a brilliant explosion called
a supernova
• Interior condenses
• May produce a hot, dense object that is
either a neutron star or a black hole

24.2 Evolutionary stages of
massive stars

Figure 24.12 C

24.2 Stellar remnants
 White
•
•

Small (some no larger than Earth)
Dense
•
•
•

•
•

dwarf

Can be more massive than the Sun
Spoonful weighs several tons
Atoms take up less space
• Electrons displaced inward
• Called degenerate matter

Hot surface
Cools to become a black dwarf

24.2 Stellar remnants (continued)
 Neutron
•

Forms from a more massive star
•
•

•
•

star

Star has more gravity
Squeezes itself smaller

Remnant of a supernova
Gravitational force collapses atoms
•
•

Electrons combine with protons to produce
neutrons
Small size

24.2 Stellar remnants (continued)
 Neutron
•

Pea size sample
•
•

•
•

star

Weighs 100 million tons
Same density as an atomic nucleus

Strong magnetic field
First one discovered in early 1970s
•
•

Pulsar (pulsating radio source)
Found in the Crab nebula (remnant of an A.D.
1054 supernova)

Crab Nebula in the
constellation Taurus

Figure 24.14

24.2 Stellar remnants (continued)
 Black
•
•

•

More dense than a neutron star
Intense surface gravity lets no light escape
As matter is pulled into it
•
•

•

hole

Becomes very hot
Emits x-rays

Likely candidate is Cygnus X-1, a strong xray source

Quiz Break

24.3 Galaxies
 Milky
•

Way galaxy

Structure
•
•

•
•

Determined by using radio telescopes
Large spiral galaxy
• About 100,000 light-years wide
• Thickness at the galactic nucleus is about
10,000 light-years
Three spiral arms of stars
Sun is 30,000 light-years from the center

Face-on view of the
Milk Way Galaxy

Figure 24.18 A

Edge-on view of the
Milk Way Galaxy

Figure 24.18 B

24.3 Galaxies (continued)
 Milky
•

Rotation
•
•
•

•

Way galaxy

Around the galactic nucleus
Outermost stars move the slowest
Sun rotates around the galactic nucleus once
about every 200 million years

Halo surrounds the galactic disk
•
•
•

Spherical
Very tenuous gas
Numerous globular clusters

24.3 Galaxies (continued)
 Other
•
•

galaxies

Existence was first proposed in mid-1700s
by Immanuel Kant
Four basic types of galaxies
•

Spiral galaxy
• Arms extending from nucleus
• About 30% of all galaxies
• Large diameter of 20,000 to 125,000 light
years
• Contains both young and old stars
• e.g., Milky Way

Great Galaxy, a spiral galaxy, in
the constellation Andromeda

Figure 24.20

24.3 Galaxies (continued)
 Other
•

galaxies

Four basic types of galaxies
•

•

Barred spiral galaxy
• Stars arranged in the shape of a bar
• Generally quite large
• About 10% of all galaxies
Elliptical galaxy
• Ellipsoidal shape
• About 60% of all galaxies
• Most are smaller than spiral galaxies;
however, they are also the largest known
galaxies

A barred spiral galaxy

Figure 24.22

24.3 Galaxies (continued)
 Other
•

galaxies

Four basic types of galaxies
•

Irregular galaxy
• Lacks symmetry
• About 10% of all galaxies
• Contains mostly young stars
• e.g., Magellanic Clouds

24.3 Galaxies (continued)
 Galactic
•
•
•

Group of galaxies
Some contain thousands of galaxies
Local Group
•
•

•

cluster

Our own group of galaxies
Contains at least 28 galaxies

Supercluster
•
•

Huge swarm of galaxies
May be the largest entity in the universe

Quiz Break

24.4 Red shifts
 Doppler
•

effect

Change in the wavelength of light emitted
by an object due to its motion
•

•

Movement away stretches the wavelength
• Longer wavelength
• Light appears redder
Movement toward “squeezes” the wavelength
• Shorter wavelength
• Light shifted toward the blue

24.4 Red shifts (continued)
 Doppler
•

effect

Amount of the Doppler shift indicates the
rate of movement
•
•

Large Doppler shift indicates a high velocity
Small Doppler shift indicates a lower velocity

 Expanding
•

universe

Most galaxies exhibit a red Doppler shift
•

Moving away

Raisin bread analogy of an
expanding universe

Figure 24.24

24.4 Red shifts (continued)
 Expanding
•

universe

Most galaxies exhibit a red Doppler shift
•

•
•
•

Far galaxies
• Exhibit the greatest shift
• Greater velocity
Discovered in 1929 by Edwin Hubble
Hubble's Law – the recessional speed of
galaxies is proportional to their distance
Accounts for red shifts

24.4 Big Bang theory
 Accounts

for galaxies moving away

from us
 Universe was once confined to a "ball"
that was
•
•

•

Supermassive
Dense
Hot

24.4 Big Bang theory (continued)
 Big

Bang marks the inception of the
universe
•
•

Occurred about 15 billion years ago
All matter and space was created

 Matter

is moving outward
 Fate of the universe
•

Two possibilities
•
•

Universe will last forever
Outward expansion sill stop and gravitational;
contraction will follow

24.4 Big Bang theory (continued)
 Fate
•

of the universe

Final fate depends on the average density
of the universe
•
•

If the density is more than the critical density,
then the universe would contract
Current estimates point to less then the critical
density and predict an ever-expanding, or
open, universe

Chapter 24Test Guidance
You will be responsible on the test for answering 3 of the following 6
questions.
1.

2.

3.
4.
5.
6.

What causes the difference between a star’s apparent
magnitude and it absolute magnitude.
List and explain the three factors that control the apparent
brightness of a star as seen from Earth.
Describe how binary stars are used to determine stellar mass.
List and describe the four basic types of galaxies.
What is Hubble’s Law, please explain in detail.
Briefly describe the Big Bang Theory (not the TV show).

End of Chapter 24


Slide 19

Lecture Outlines
PowerPoint

Chapter 24
Earth Science 11e
Tarbuck/Lutgens
Modified for educational
purposes only
By S. Koziol 12-8-2010

© 2006 Pearson Prentice Hall

Earth Science, 11e
Beyond Our
Solar System
Chapter 24

24.1 Properties of stars
 Distance
•
•

Measuring a star's distance can be very
difficult
Stellar parallax
•
•
•

•
•

Used for measuring distance to a star
Apparent shift in a star's position due to the
orbital motion of Earth
Measured as an angle
Near stars have the largest parallax
Largest parallax is less than one second of arc

24. 1 Properties of stars
(continued)

 Distance
•
•

Distances to the stars are very large
Units of measurement
•
•

•

Kilometers or astronomical units are too
cumbersome to use
Light-year is used most often
• Distance that light travels in 1 year
• One light-year is 9.5 trillion km (5.8 trillion
miles)

Other methods for measuring distance are
also used

24. 1 Properties of stars
(continued)

 Stellar
•

Controlled by three factors
•

•
•

•

brightness

Size
Temperature
Distance

Magnitude
•

Measure of a star's brightness

24.1 Properties of stars
(continued)

 Stellar
•

brightness

Magnitude
•

Two types of measurement
• Apparent magnitude
• Brightness when a star is viewed from
Earth
• Decreases with distance
• Numbers are used to designate
magnitudes - dim stars have large
numbers and negative numbers are also
used

24.1 Properties of stars
(continued)

 Stellar
•

brightness

Magnitude
•

Two types of measurement
• Absolute magnitude
• "True" or intrinsic brightness of a star
• Brightness at a standard distance of
32.6 light-years
• Most stars' absolute magnitudes are
between -5 and +15

24.1 Properties of stars
(continued)

 Color
•

Hot star
•

•
•

•

and temperature

Temperature above 30,000 K
Emits short-wavelength light
Appears blue

Cool star
•
•
•

Temperature less than 3000 K
Emits longer-wavelength light
Appears red

24.1 Properties of stars
(continued)

 Color
•

and temperature

Between 5000 and 6000 K
•
•

Stars appear yellow
e.g., Sun

 Binary
•

stars and stellar mass

Binary stars
•

Two stars orbiting one another
• Stars are held together by mutual
gravitation
• Both orbit around a common center of mass

24.1 Properties of stars (continued)
 Binary
•

Binary stars
•

•
•

•

stars and stellar mass

Visual binaries are resolved telescopically
More than 50% of the stars in the universe are
binary stars
Used to determine stellar mass

Stellar mass
•

Determined using binary stars – the center of
mass is closest to the most massive star

Binary stars
orbit each
other around
their common
center of
mass
Figure 24.4

24.1 Properties of stars (continued)
 Binary
•

stars and stellar mass

Stellar mass
•

Mass of most stars is between one-tenth and
fifty times the mass of the Sun

24.1 Hertzsprung-Russell
diagram
 Shows
•
•

the relation between stellar

Brightness (absolute magnitude) and
Temperature

 Diagram

is made by plotting (graphing)
each star's
•
•

Luminosity (brightness) and
Temperature

24.1 Hertzsprung-Russell
diagram (continued)
 Parts
•

Main-sequence stars
•

•
•

•

of an H-R diagram

90% of all stars
Band through the center of the H-R diagram
Sun is in the main-sequence

Giants (or red giants)
•
•
•

Very luminous
Large
Upper-right on the H-R diagram

24.1 Hertzsprung-Russell
diagram (continued)
 Parts
•

Giants (or red giants)
•

•

•

of an H-R diagram

Very large giants are called supergiants
Only a few percent of all stars

White dwarfs
•
•

•
•
•

Fainter than main-sequence stars
Small (approximate the size of Earth)
Lower-central area on the H-R diagram
Not all are white in color
Perhaps 10% of all stars

Idealized HertzsprungRussell diagram

Figure 24.5

Quiz Break

24.2 Variable stars
 Stars

that fluctuate in brightness
 Types of variable stars
•

Pulsating variables
•
•

•

Fluctuate regularly in brightness
Expand and contract in size

Eruptive variables
•
•
•

Explosive event
Sudden brightening
Called a nova

24.2 Interstellar matter
 Between

the stars is "the vacuum of

space"
 Nebula
•
•

Cloud of dust and gases
Two major types of nebulae
•

Bright nebula
• Glows if it close to a very hot star
• Two types of bright nebulae
• Emission nebula
• Reflection nebula

The Orion Nebula is a wellknown emission nebula

Figure 24.8

A faint blue reflection nebula in
the Pleiades star cluster

Figure 24.9

24.2 Interstellar matter (continued)
 Nebula
•

Two major types of nebulae
•

Dark nebula
• Not close to any bright star
• Appear dark
• Contains the material that forms stars and
planets

24.2 Stellar evolution
 Stars

exist because of gravity
 Two opposing forces in a star are
•
•

Gravity – contracts
Thermal nuclear energy – expands

 Stages
•

Birth
•

•
•
•
•

In dark, cool, interstellar clouds
Gravity contracts the cloud
Temperature rises
Radiates long-wavelength (red) light
Becomes a protostar

24.2 Stellar evolution (continued)
 Stages
•

Protostar
•
•
•

•
•
•
•

Gravitational contraction of gaseous cloud
continues
Core reaches 10 million K
Hydrogen nuclei fuse
• Become helium nuclei
• Process is called hydrogen burning
Energy is released
Outward pressure increases
Outward pressure balanced by gravity pulling in
Star becomes a stable main-sequence star

24.2 Stellar evolution (continued)
 Stages
•

Main-sequence stage
•

Stars age at different rates
• Massive stars use fuel faster and exist for
only a few million years
• Small stars use fuel slowly and exist for
perhaps hundreds of billions of years

•

90% of a star's life is in the main-sequence

24.2 Stellar evolution (continued)
 Stages
•

Red giant stage
•
•

•
•
•

Hydrogen burning migrates outward
Star's outer envelope expands
• Surface cools
• Surface becomes red
Core is collapsing as helium is converted to
carbon
Eventually all nuclear fuel is used
Gravity squeezes the star

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Low-mass star
• 0.5 solar mass
• Red giant collapses
• Becomes a white dwarf

24.2 Evolutionary stages of
low mass stars

Figure 24.12 A

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Medium-mass star
• Between 0.5 and 3 solar masses
• Red giant collapses
• Planetary nebula forms
• Becomes a white dwarf

24.2 Evolutionary stages of
medium mass stars

Figure 24.12 B

H-R diagram showing
stellar evolution

Figure 24.11

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Massive star
• Over 3 solar masses
• Short life span
• Terminates in a brilliant explosion called
a supernova
• Interior condenses
• May produce a hot, dense object that is
either a neutron star or a black hole

24.2 Evolutionary stages of
massive stars

Figure 24.12 C

24.2 Stellar remnants
 White
•
•

Small (some no larger than Earth)
Dense
•
•
•

•
•

dwarf

Can be more massive than the Sun
Spoonful weighs several tons
Atoms take up less space
• Electrons displaced inward
• Called degenerate matter

Hot surface
Cools to become a black dwarf

24.2 Stellar remnants (continued)
 Neutron
•

Forms from a more massive star
•
•

•
•

star

Star has more gravity
Squeezes itself smaller

Remnant of a supernova
Gravitational force collapses atoms
•
•

Electrons combine with protons to produce
neutrons
Small size

24.2 Stellar remnants (continued)
 Neutron
•

Pea size sample
•
•

•
•

star

Weighs 100 million tons
Same density as an atomic nucleus

Strong magnetic field
First one discovered in early 1970s
•
•

Pulsar (pulsating radio source)
Found in the Crab nebula (remnant of an A.D.
1054 supernova)

Crab Nebula in the
constellation Taurus

Figure 24.14

24.2 Stellar remnants (continued)
 Black
•
•

•

More dense than a neutron star
Intense surface gravity lets no light escape
As matter is pulled into it
•
•

•

hole

Becomes very hot
Emits x-rays

Likely candidate is Cygnus X-1, a strong xray source

Quiz Break

24.3 Galaxies
 Milky
•

Way galaxy

Structure
•
•

•
•

Determined by using radio telescopes
Large spiral galaxy
• About 100,000 light-years wide
• Thickness at the galactic nucleus is about
10,000 light-years
Three spiral arms of stars
Sun is 30,000 light-years from the center

Face-on view of the
Milk Way Galaxy

Figure 24.18 A

Edge-on view of the
Milk Way Galaxy

Figure 24.18 B

24.3 Galaxies (continued)
 Milky
•

Rotation
•
•
•

•

Way galaxy

Around the galactic nucleus
Outermost stars move the slowest
Sun rotates around the galactic nucleus once
about every 200 million years

Halo surrounds the galactic disk
•
•
•

Spherical
Very tenuous gas
Numerous globular clusters

24.3 Galaxies (continued)
 Other
•
•

galaxies

Existence was first proposed in mid-1700s
by Immanuel Kant
Four basic types of galaxies
•

Spiral galaxy
• Arms extending from nucleus
• About 30% of all galaxies
• Large diameter of 20,000 to 125,000 light
years
• Contains both young and old stars
• e.g., Milky Way

Great Galaxy, a spiral galaxy, in
the constellation Andromeda

Figure 24.20

24.3 Galaxies (continued)
 Other
•

galaxies

Four basic types of galaxies
•

•

Barred spiral galaxy
• Stars arranged in the shape of a bar
• Generally quite large
• About 10% of all galaxies
Elliptical galaxy
• Ellipsoidal shape
• About 60% of all galaxies
• Most are smaller than spiral galaxies;
however, they are also the largest known
galaxies

A barred spiral galaxy

Figure 24.22

24.3 Galaxies (continued)
 Other
•

galaxies

Four basic types of galaxies
•

Irregular galaxy
• Lacks symmetry
• About 10% of all galaxies
• Contains mostly young stars
• e.g., Magellanic Clouds

24.3 Galaxies (continued)
 Galactic
•
•
•

Group of galaxies
Some contain thousands of galaxies
Local Group
•
•

•

cluster

Our own group of galaxies
Contains at least 28 galaxies

Supercluster
•
•

Huge swarm of galaxies
May be the largest entity in the universe

Quiz Break

24.4 Red shifts
 Doppler
•

effect

Change in the wavelength of light emitted
by an object due to its motion
•

•

Movement away stretches the wavelength
• Longer wavelength
• Light appears redder
Movement toward “squeezes” the wavelength
• Shorter wavelength
• Light shifted toward the blue

24.4 Red shifts (continued)
 Doppler
•

effect

Amount of the Doppler shift indicates the
rate of movement
•
•

Large Doppler shift indicates a high velocity
Small Doppler shift indicates a lower velocity

 Expanding
•

universe

Most galaxies exhibit a red Doppler shift
•

Moving away

Raisin bread analogy of an
expanding universe

Figure 24.24

24.4 Red shifts (continued)
 Expanding
•

universe

Most galaxies exhibit a red Doppler shift
•

•
•
•

Far galaxies
• Exhibit the greatest shift
• Greater velocity
Discovered in 1929 by Edwin Hubble
Hubble's Law – the recessional speed of
galaxies is proportional to their distance
Accounts for red shifts

24.4 Big Bang theory
 Accounts

for galaxies moving away

from us
 Universe was once confined to a "ball"
that was
•
•

•

Supermassive
Dense
Hot

24.4 Big Bang theory (continued)
 Big

Bang marks the inception of the
universe
•
•

Occurred about 15 billion years ago
All matter and space was created

 Matter

is moving outward
 Fate of the universe
•

Two possibilities
•
•

Universe will last forever
Outward expansion sill stop and gravitational;
contraction will follow

24.4 Big Bang theory (continued)
 Fate
•

of the universe

Final fate depends on the average density
of the universe
•
•

If the density is more than the critical density,
then the universe would contract
Current estimates point to less then the critical
density and predict an ever-expanding, or
open, universe

Chapter 24Test Guidance
You will be responsible on the test for answering 3 of the following 6
questions.
1.

2.

3.
4.
5.
6.

What causes the difference between a star’s apparent
magnitude and it absolute magnitude.
List and explain the three factors that control the apparent
brightness of a star as seen from Earth.
Describe how binary stars are used to determine stellar mass.
List and describe the four basic types of galaxies.
What is Hubble’s Law, please explain in detail.
Briefly describe the Big Bang Theory (not the TV show).

End of Chapter 24


Slide 20

Lecture Outlines
PowerPoint

Chapter 24
Earth Science 11e
Tarbuck/Lutgens
Modified for educational
purposes only
By S. Koziol 12-8-2010

© 2006 Pearson Prentice Hall

Earth Science, 11e
Beyond Our
Solar System
Chapter 24

24.1 Properties of stars
 Distance
•
•

Measuring a star's distance can be very
difficult
Stellar parallax
•
•
•

•
•

Used for measuring distance to a star
Apparent shift in a star's position due to the
orbital motion of Earth
Measured as an angle
Near stars have the largest parallax
Largest parallax is less than one second of arc

24. 1 Properties of stars
(continued)

 Distance
•
•

Distances to the stars are very large
Units of measurement
•
•

•

Kilometers or astronomical units are too
cumbersome to use
Light-year is used most often
• Distance that light travels in 1 year
• One light-year is 9.5 trillion km (5.8 trillion
miles)

Other methods for measuring distance are
also used

24. 1 Properties of stars
(continued)

 Stellar
•

Controlled by three factors
•

•
•

•

brightness

Size
Temperature
Distance

Magnitude
•

Measure of a star's brightness

24.1 Properties of stars
(continued)

 Stellar
•

brightness

Magnitude
•

Two types of measurement
• Apparent magnitude
• Brightness when a star is viewed from
Earth
• Decreases with distance
• Numbers are used to designate
magnitudes - dim stars have large
numbers and negative numbers are also
used

24.1 Properties of stars
(continued)

 Stellar
•

brightness

Magnitude
•

Two types of measurement
• Absolute magnitude
• "True" or intrinsic brightness of a star
• Brightness at a standard distance of
32.6 light-years
• Most stars' absolute magnitudes are
between -5 and +15

24.1 Properties of stars
(continued)

 Color
•

Hot star
•

•
•

•

and temperature

Temperature above 30,000 K
Emits short-wavelength light
Appears blue

Cool star
•
•
•

Temperature less than 3000 K
Emits longer-wavelength light
Appears red

24.1 Properties of stars
(continued)

 Color
•

and temperature

Between 5000 and 6000 K
•
•

Stars appear yellow
e.g., Sun

 Binary
•

stars and stellar mass

Binary stars
•

Two stars orbiting one another
• Stars are held together by mutual
gravitation
• Both orbit around a common center of mass

24.1 Properties of stars (continued)
 Binary
•

Binary stars
•

•
•

•

stars and stellar mass

Visual binaries are resolved telescopically
More than 50% of the stars in the universe are
binary stars
Used to determine stellar mass

Stellar mass
•

Determined using binary stars – the center of
mass is closest to the most massive star

Binary stars
orbit each
other around
their common
center of
mass
Figure 24.4

24.1 Properties of stars (continued)
 Binary
•

stars and stellar mass

Stellar mass
•

Mass of most stars is between one-tenth and
fifty times the mass of the Sun

24.1 Hertzsprung-Russell
diagram
 Shows
•
•

the relation between stellar

Brightness (absolute magnitude) and
Temperature

 Diagram

is made by plotting (graphing)
each star's
•
•

Luminosity (brightness) and
Temperature

24.1 Hertzsprung-Russell
diagram (continued)
 Parts
•

Main-sequence stars
•

•
•

•

of an H-R diagram

90% of all stars
Band through the center of the H-R diagram
Sun is in the main-sequence

Giants (or red giants)
•
•
•

Very luminous
Large
Upper-right on the H-R diagram

24.1 Hertzsprung-Russell
diagram (continued)
 Parts
•

Giants (or red giants)
•

•

•

of an H-R diagram

Very large giants are called supergiants
Only a few percent of all stars

White dwarfs
•
•

•
•
•

Fainter than main-sequence stars
Small (approximate the size of Earth)
Lower-central area on the H-R diagram
Not all are white in color
Perhaps 10% of all stars

Idealized HertzsprungRussell diagram

Figure 24.5

Quiz Break

24.2 Variable stars
 Stars

that fluctuate in brightness
 Types of variable stars
•

Pulsating variables
•
•

•

Fluctuate regularly in brightness
Expand and contract in size

Eruptive variables
•
•
•

Explosive event
Sudden brightening
Called a nova

24.2 Interstellar matter
 Between

the stars is "the vacuum of

space"
 Nebula
•
•

Cloud of dust and gases
Two major types of nebulae
•

Bright nebula
• Glows if it close to a very hot star
• Two types of bright nebulae
• Emission nebula
• Reflection nebula

The Orion Nebula is a wellknown emission nebula

Figure 24.8

A faint blue reflection nebula in
the Pleiades star cluster

Figure 24.9

24.2 Interstellar matter (continued)
 Nebula
•

Two major types of nebulae
•

Dark nebula
• Not close to any bright star
• Appear dark
• Contains the material that forms stars and
planets

24.2 Stellar evolution
 Stars

exist because of gravity
 Two opposing forces in a star are
•
•

Gravity – contracts
Thermal nuclear energy – expands

 Stages
•

Birth
•

•
•
•
•

In dark, cool, interstellar clouds
Gravity contracts the cloud
Temperature rises
Radiates long-wavelength (red) light
Becomes a protostar

24.2 Stellar evolution (continued)
 Stages
•

Protostar
•
•
•

•
•
•
•

Gravitational contraction of gaseous cloud
continues
Core reaches 10 million K
Hydrogen nuclei fuse
• Become helium nuclei
• Process is called hydrogen burning
Energy is released
Outward pressure increases
Outward pressure balanced by gravity pulling in
Star becomes a stable main-sequence star

24.2 Stellar evolution (continued)
 Stages
•

Main-sequence stage
•

Stars age at different rates
• Massive stars use fuel faster and exist for
only a few million years
• Small stars use fuel slowly and exist for
perhaps hundreds of billions of years

•

90% of a star's life is in the main-sequence

24.2 Stellar evolution (continued)
 Stages
•

Red giant stage
•
•

•
•
•

Hydrogen burning migrates outward
Star's outer envelope expands
• Surface cools
• Surface becomes red
Core is collapsing as helium is converted to
carbon
Eventually all nuclear fuel is used
Gravity squeezes the star

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Low-mass star
• 0.5 solar mass
• Red giant collapses
• Becomes a white dwarf

24.2 Evolutionary stages of
low mass stars

Figure 24.12 A

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Medium-mass star
• Between 0.5 and 3 solar masses
• Red giant collapses
• Planetary nebula forms
• Becomes a white dwarf

24.2 Evolutionary stages of
medium mass stars

Figure 24.12 B

H-R diagram showing
stellar evolution

Figure 24.11

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Massive star
• Over 3 solar masses
• Short life span
• Terminates in a brilliant explosion called
a supernova
• Interior condenses
• May produce a hot, dense object that is
either a neutron star or a black hole

24.2 Evolutionary stages of
massive stars

Figure 24.12 C

24.2 Stellar remnants
 White
•
•

Small (some no larger than Earth)
Dense
•
•
•

•
•

dwarf

Can be more massive than the Sun
Spoonful weighs several tons
Atoms take up less space
• Electrons displaced inward
• Called degenerate matter

Hot surface
Cools to become a black dwarf

24.2 Stellar remnants (continued)
 Neutron
•

Forms from a more massive star
•
•

•
•

star

Star has more gravity
Squeezes itself smaller

Remnant of a supernova
Gravitational force collapses atoms
•
•

Electrons combine with protons to produce
neutrons
Small size

24.2 Stellar remnants (continued)
 Neutron
•

Pea size sample
•
•

•
•

star

Weighs 100 million tons
Same density as an atomic nucleus

Strong magnetic field
First one discovered in early 1970s
•
•

Pulsar (pulsating radio source)
Found in the Crab nebula (remnant of an A.D.
1054 supernova)

Crab Nebula in the
constellation Taurus

Figure 24.14

24.2 Stellar remnants (continued)
 Black
•
•

•

More dense than a neutron star
Intense surface gravity lets no light escape
As matter is pulled into it
•
•

•

hole

Becomes very hot
Emits x-rays

Likely candidate is Cygnus X-1, a strong xray source

Quiz Break

24.3 Galaxies
 Milky
•

Way galaxy

Structure
•
•

•
•

Determined by using radio telescopes
Large spiral galaxy
• About 100,000 light-years wide
• Thickness at the galactic nucleus is about
10,000 light-years
Three spiral arms of stars
Sun is 30,000 light-years from the center

Face-on view of the
Milk Way Galaxy

Figure 24.18 A

Edge-on view of the
Milk Way Galaxy

Figure 24.18 B

24.3 Galaxies (continued)
 Milky
•

Rotation
•
•
•

•

Way galaxy

Around the galactic nucleus
Outermost stars move the slowest
Sun rotates around the galactic nucleus once
about every 200 million years

Halo surrounds the galactic disk
•
•
•

Spherical
Very tenuous gas
Numerous globular clusters

24.3 Galaxies (continued)
 Other
•
•

galaxies

Existence was first proposed in mid-1700s
by Immanuel Kant
Four basic types of galaxies
•

Spiral galaxy
• Arms extending from nucleus
• About 30% of all galaxies
• Large diameter of 20,000 to 125,000 light
years
• Contains both young and old stars
• e.g., Milky Way

Great Galaxy, a spiral galaxy, in
the constellation Andromeda

Figure 24.20

24.3 Galaxies (continued)
 Other
•

galaxies

Four basic types of galaxies
•

•

Barred spiral galaxy
• Stars arranged in the shape of a bar
• Generally quite large
• About 10% of all galaxies
Elliptical galaxy
• Ellipsoidal shape
• About 60% of all galaxies
• Most are smaller than spiral galaxies;
however, they are also the largest known
galaxies

A barred spiral galaxy

Figure 24.22

24.3 Galaxies (continued)
 Other
•

galaxies

Four basic types of galaxies
•

Irregular galaxy
• Lacks symmetry
• About 10% of all galaxies
• Contains mostly young stars
• e.g., Magellanic Clouds

24.3 Galaxies (continued)
 Galactic
•
•
•

Group of galaxies
Some contain thousands of galaxies
Local Group
•
•

•

cluster

Our own group of galaxies
Contains at least 28 galaxies

Supercluster
•
•

Huge swarm of galaxies
May be the largest entity in the universe

Quiz Break

24.4 Red shifts
 Doppler
•

effect

Change in the wavelength of light emitted
by an object due to its motion
•

•

Movement away stretches the wavelength
• Longer wavelength
• Light appears redder
Movement toward “squeezes” the wavelength
• Shorter wavelength
• Light shifted toward the blue

24.4 Red shifts (continued)
 Doppler
•

effect

Amount of the Doppler shift indicates the
rate of movement
•
•

Large Doppler shift indicates a high velocity
Small Doppler shift indicates a lower velocity

 Expanding
•

universe

Most galaxies exhibit a red Doppler shift
•

Moving away

Raisin bread analogy of an
expanding universe

Figure 24.24

24.4 Red shifts (continued)
 Expanding
•

universe

Most galaxies exhibit a red Doppler shift
•

•
•
•

Far galaxies
• Exhibit the greatest shift
• Greater velocity
Discovered in 1929 by Edwin Hubble
Hubble's Law – the recessional speed of
galaxies is proportional to their distance
Accounts for red shifts

24.4 Big Bang theory
 Accounts

for galaxies moving away

from us
 Universe was once confined to a "ball"
that was
•
•

•

Supermassive
Dense
Hot

24.4 Big Bang theory (continued)
 Big

Bang marks the inception of the
universe
•
•

Occurred about 15 billion years ago
All matter and space was created

 Matter

is moving outward
 Fate of the universe
•

Two possibilities
•
•

Universe will last forever
Outward expansion sill stop and gravitational;
contraction will follow

24.4 Big Bang theory (continued)
 Fate
•

of the universe

Final fate depends on the average density
of the universe
•
•

If the density is more than the critical density,
then the universe would contract
Current estimates point to less then the critical
density and predict an ever-expanding, or
open, universe

Chapter 24Test Guidance
You will be responsible on the test for answering 3 of the following 6
questions.
1.

2.

3.
4.
5.
6.

What causes the difference between a star’s apparent
magnitude and it absolute magnitude.
List and explain the three factors that control the apparent
brightness of a star as seen from Earth.
Describe how binary stars are used to determine stellar mass.
List and describe the four basic types of galaxies.
What is Hubble’s Law, please explain in detail.
Briefly describe the Big Bang Theory (not the TV show).

End of Chapter 24


Slide 21

Lecture Outlines
PowerPoint

Chapter 24
Earth Science 11e
Tarbuck/Lutgens
Modified for educational
purposes only
By S. Koziol 12-8-2010

© 2006 Pearson Prentice Hall

Earth Science, 11e
Beyond Our
Solar System
Chapter 24

24.1 Properties of stars
 Distance
•
•

Measuring a star's distance can be very
difficult
Stellar parallax
•
•
•

•
•

Used for measuring distance to a star
Apparent shift in a star's position due to the
orbital motion of Earth
Measured as an angle
Near stars have the largest parallax
Largest parallax is less than one second of arc

24. 1 Properties of stars
(continued)

 Distance
•
•

Distances to the stars are very large
Units of measurement
•
•

•

Kilometers or astronomical units are too
cumbersome to use
Light-year is used most often
• Distance that light travels in 1 year
• One light-year is 9.5 trillion km (5.8 trillion
miles)

Other methods for measuring distance are
also used

24. 1 Properties of stars
(continued)

 Stellar
•

Controlled by three factors
•

•
•

•

brightness

Size
Temperature
Distance

Magnitude
•

Measure of a star's brightness

24.1 Properties of stars
(continued)

 Stellar
•

brightness

Magnitude
•

Two types of measurement
• Apparent magnitude
• Brightness when a star is viewed from
Earth
• Decreases with distance
• Numbers are used to designate
magnitudes - dim stars have large
numbers and negative numbers are also
used

24.1 Properties of stars
(continued)

 Stellar
•

brightness

Magnitude
•

Two types of measurement
• Absolute magnitude
• "True" or intrinsic brightness of a star
• Brightness at a standard distance of
32.6 light-years
• Most stars' absolute magnitudes are
between -5 and +15

24.1 Properties of stars
(continued)

 Color
•

Hot star
•

•
•

•

and temperature

Temperature above 30,000 K
Emits short-wavelength light
Appears blue

Cool star
•
•
•

Temperature less than 3000 K
Emits longer-wavelength light
Appears red

24.1 Properties of stars
(continued)

 Color
•

and temperature

Between 5000 and 6000 K
•
•

Stars appear yellow
e.g., Sun

 Binary
•

stars and stellar mass

Binary stars
•

Two stars orbiting one another
• Stars are held together by mutual
gravitation
• Both orbit around a common center of mass

24.1 Properties of stars (continued)
 Binary
•

Binary stars
•

•
•

•

stars and stellar mass

Visual binaries are resolved telescopically
More than 50% of the stars in the universe are
binary stars
Used to determine stellar mass

Stellar mass
•

Determined using binary stars – the center of
mass is closest to the most massive star

Binary stars
orbit each
other around
their common
center of
mass
Figure 24.4

24.1 Properties of stars (continued)
 Binary
•

stars and stellar mass

Stellar mass
•

Mass of most stars is between one-tenth and
fifty times the mass of the Sun

24.1 Hertzsprung-Russell
diagram
 Shows
•
•

the relation between stellar

Brightness (absolute magnitude) and
Temperature

 Diagram

is made by plotting (graphing)
each star's
•
•

Luminosity (brightness) and
Temperature

24.1 Hertzsprung-Russell
diagram (continued)
 Parts
•

Main-sequence stars
•

•
•

•

of an H-R diagram

90% of all stars
Band through the center of the H-R diagram
Sun is in the main-sequence

Giants (or red giants)
•
•
•

Very luminous
Large
Upper-right on the H-R diagram

24.1 Hertzsprung-Russell
diagram (continued)
 Parts
•

Giants (or red giants)
•

•

•

of an H-R diagram

Very large giants are called supergiants
Only a few percent of all stars

White dwarfs
•
•

•
•
•

Fainter than main-sequence stars
Small (approximate the size of Earth)
Lower-central area on the H-R diagram
Not all are white in color
Perhaps 10% of all stars

Idealized HertzsprungRussell diagram

Figure 24.5

Quiz Break

24.2 Variable stars
 Stars

that fluctuate in brightness
 Types of variable stars
•

Pulsating variables
•
•

•

Fluctuate regularly in brightness
Expand and contract in size

Eruptive variables
•
•
•

Explosive event
Sudden brightening
Called a nova

24.2 Interstellar matter
 Between

the stars is "the vacuum of

space"
 Nebula
•
•

Cloud of dust and gases
Two major types of nebulae
•

Bright nebula
• Glows if it close to a very hot star
• Two types of bright nebulae
• Emission nebula
• Reflection nebula

The Orion Nebula is a wellknown emission nebula

Figure 24.8

A faint blue reflection nebula in
the Pleiades star cluster

Figure 24.9

24.2 Interstellar matter (continued)
 Nebula
•

Two major types of nebulae
•

Dark nebula
• Not close to any bright star
• Appear dark
• Contains the material that forms stars and
planets

24.2 Stellar evolution
 Stars

exist because of gravity
 Two opposing forces in a star are
•
•

Gravity – contracts
Thermal nuclear energy – expands

 Stages
•

Birth
•

•
•
•
•

In dark, cool, interstellar clouds
Gravity contracts the cloud
Temperature rises
Radiates long-wavelength (red) light
Becomes a protostar

24.2 Stellar evolution (continued)
 Stages
•

Protostar
•
•
•

•
•
•
•

Gravitational contraction of gaseous cloud
continues
Core reaches 10 million K
Hydrogen nuclei fuse
• Become helium nuclei
• Process is called hydrogen burning
Energy is released
Outward pressure increases
Outward pressure balanced by gravity pulling in
Star becomes a stable main-sequence star

24.2 Stellar evolution (continued)
 Stages
•

Main-sequence stage
•

Stars age at different rates
• Massive stars use fuel faster and exist for
only a few million years
• Small stars use fuel slowly and exist for
perhaps hundreds of billions of years

•

90% of a star's life is in the main-sequence

24.2 Stellar evolution (continued)
 Stages
•

Red giant stage
•
•

•
•
•

Hydrogen burning migrates outward
Star's outer envelope expands
• Surface cools
• Surface becomes red
Core is collapsing as helium is converted to
carbon
Eventually all nuclear fuel is used
Gravity squeezes the star

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Low-mass star
• 0.5 solar mass
• Red giant collapses
• Becomes a white dwarf

24.2 Evolutionary stages of
low mass stars

Figure 24.12 A

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Medium-mass star
• Between 0.5 and 3 solar masses
• Red giant collapses
• Planetary nebula forms
• Becomes a white dwarf

24.2 Evolutionary stages of
medium mass stars

Figure 24.12 B

H-R diagram showing
stellar evolution

Figure 24.11

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Massive star
• Over 3 solar masses
• Short life span
• Terminates in a brilliant explosion called
a supernova
• Interior condenses
• May produce a hot, dense object that is
either a neutron star or a black hole

24.2 Evolutionary stages of
massive stars

Figure 24.12 C

24.2 Stellar remnants
 White
•
•

Small (some no larger than Earth)
Dense
•
•
•

•
•

dwarf

Can be more massive than the Sun
Spoonful weighs several tons
Atoms take up less space
• Electrons displaced inward
• Called degenerate matter

Hot surface
Cools to become a black dwarf

24.2 Stellar remnants (continued)
 Neutron
•

Forms from a more massive star
•
•

•
•

star

Star has more gravity
Squeezes itself smaller

Remnant of a supernova
Gravitational force collapses atoms
•
•

Electrons combine with protons to produce
neutrons
Small size

24.2 Stellar remnants (continued)
 Neutron
•

Pea size sample
•
•

•
•

star

Weighs 100 million tons
Same density as an atomic nucleus

Strong magnetic field
First one discovered in early 1970s
•
•

Pulsar (pulsating radio source)
Found in the Crab nebula (remnant of an A.D.
1054 supernova)

Crab Nebula in the
constellation Taurus

Figure 24.14

24.2 Stellar remnants (continued)
 Black
•
•

•

More dense than a neutron star
Intense surface gravity lets no light escape
As matter is pulled into it
•
•

•

hole

Becomes very hot
Emits x-rays

Likely candidate is Cygnus X-1, a strong xray source

Quiz Break

24.3 Galaxies
 Milky
•

Way galaxy

Structure
•
•

•
•

Determined by using radio telescopes
Large spiral galaxy
• About 100,000 light-years wide
• Thickness at the galactic nucleus is about
10,000 light-years
Three spiral arms of stars
Sun is 30,000 light-years from the center

Face-on view of the
Milk Way Galaxy

Figure 24.18 A

Edge-on view of the
Milk Way Galaxy

Figure 24.18 B

24.3 Galaxies (continued)
 Milky
•

Rotation
•
•
•

•

Way galaxy

Around the galactic nucleus
Outermost stars move the slowest
Sun rotates around the galactic nucleus once
about every 200 million years

Halo surrounds the galactic disk
•
•
•

Spherical
Very tenuous gas
Numerous globular clusters

24.3 Galaxies (continued)
 Other
•
•

galaxies

Existence was first proposed in mid-1700s
by Immanuel Kant
Four basic types of galaxies
•

Spiral galaxy
• Arms extending from nucleus
• About 30% of all galaxies
• Large diameter of 20,000 to 125,000 light
years
• Contains both young and old stars
• e.g., Milky Way

Great Galaxy, a spiral galaxy, in
the constellation Andromeda

Figure 24.20

24.3 Galaxies (continued)
 Other
•

galaxies

Four basic types of galaxies
•

•

Barred spiral galaxy
• Stars arranged in the shape of a bar
• Generally quite large
• About 10% of all galaxies
Elliptical galaxy
• Ellipsoidal shape
• About 60% of all galaxies
• Most are smaller than spiral galaxies;
however, they are also the largest known
galaxies

A barred spiral galaxy

Figure 24.22

24.3 Galaxies (continued)
 Other
•

galaxies

Four basic types of galaxies
•

Irregular galaxy
• Lacks symmetry
• About 10% of all galaxies
• Contains mostly young stars
• e.g., Magellanic Clouds

24.3 Galaxies (continued)
 Galactic
•
•
•

Group of galaxies
Some contain thousands of galaxies
Local Group
•
•

•

cluster

Our own group of galaxies
Contains at least 28 galaxies

Supercluster
•
•

Huge swarm of galaxies
May be the largest entity in the universe

Quiz Break

24.4 Red shifts
 Doppler
•

effect

Change in the wavelength of light emitted
by an object due to its motion
•

•

Movement away stretches the wavelength
• Longer wavelength
• Light appears redder
Movement toward “squeezes” the wavelength
• Shorter wavelength
• Light shifted toward the blue

24.4 Red shifts (continued)
 Doppler
•

effect

Amount of the Doppler shift indicates the
rate of movement
•
•

Large Doppler shift indicates a high velocity
Small Doppler shift indicates a lower velocity

 Expanding
•

universe

Most galaxies exhibit a red Doppler shift
•

Moving away

Raisin bread analogy of an
expanding universe

Figure 24.24

24.4 Red shifts (continued)
 Expanding
•

universe

Most galaxies exhibit a red Doppler shift
•

•
•
•

Far galaxies
• Exhibit the greatest shift
• Greater velocity
Discovered in 1929 by Edwin Hubble
Hubble's Law – the recessional speed of
galaxies is proportional to their distance
Accounts for red shifts

24.4 Big Bang theory
 Accounts

for galaxies moving away

from us
 Universe was once confined to a "ball"
that was
•
•

•

Supermassive
Dense
Hot

24.4 Big Bang theory (continued)
 Big

Bang marks the inception of the
universe
•
•

Occurred about 15 billion years ago
All matter and space was created

 Matter

is moving outward
 Fate of the universe
•

Two possibilities
•
•

Universe will last forever
Outward expansion sill stop and gravitational;
contraction will follow

24.4 Big Bang theory (continued)
 Fate
•

of the universe

Final fate depends on the average density
of the universe
•
•

If the density is more than the critical density,
then the universe would contract
Current estimates point to less then the critical
density and predict an ever-expanding, or
open, universe

Chapter 24Test Guidance
You will be responsible on the test for answering 3 of the following 6
questions.
1.

2.

3.
4.
5.
6.

What causes the difference between a star’s apparent
magnitude and it absolute magnitude.
List and explain the three factors that control the apparent
brightness of a star as seen from Earth.
Describe how binary stars are used to determine stellar mass.
List and describe the four basic types of galaxies.
What is Hubble’s Law, please explain in detail.
Briefly describe the Big Bang Theory (not the TV show).

End of Chapter 24


Slide 22

Lecture Outlines
PowerPoint

Chapter 24
Earth Science 11e
Tarbuck/Lutgens
Modified for educational
purposes only
By S. Koziol 12-8-2010

© 2006 Pearson Prentice Hall

Earth Science, 11e
Beyond Our
Solar System
Chapter 24

24.1 Properties of stars
 Distance
•
•

Measuring a star's distance can be very
difficult
Stellar parallax
•
•
•

•
•

Used for measuring distance to a star
Apparent shift in a star's position due to the
orbital motion of Earth
Measured as an angle
Near stars have the largest parallax
Largest parallax is less than one second of arc

24. 1 Properties of stars
(continued)

 Distance
•
•

Distances to the stars are very large
Units of measurement
•
•

•

Kilometers or astronomical units are too
cumbersome to use
Light-year is used most often
• Distance that light travels in 1 year
• One light-year is 9.5 trillion km (5.8 trillion
miles)

Other methods for measuring distance are
also used

24. 1 Properties of stars
(continued)

 Stellar
•

Controlled by three factors
•

•
•

•

brightness

Size
Temperature
Distance

Magnitude
•

Measure of a star's brightness

24.1 Properties of stars
(continued)

 Stellar
•

brightness

Magnitude
•

Two types of measurement
• Apparent magnitude
• Brightness when a star is viewed from
Earth
• Decreases with distance
• Numbers are used to designate
magnitudes - dim stars have large
numbers and negative numbers are also
used

24.1 Properties of stars
(continued)

 Stellar
•

brightness

Magnitude
•

Two types of measurement
• Absolute magnitude
• "True" or intrinsic brightness of a star
• Brightness at a standard distance of
32.6 light-years
• Most stars' absolute magnitudes are
between -5 and +15

24.1 Properties of stars
(continued)

 Color
•

Hot star
•

•
•

•

and temperature

Temperature above 30,000 K
Emits short-wavelength light
Appears blue

Cool star
•
•
•

Temperature less than 3000 K
Emits longer-wavelength light
Appears red

24.1 Properties of stars
(continued)

 Color
•

and temperature

Between 5000 and 6000 K
•
•

Stars appear yellow
e.g., Sun

 Binary
•

stars and stellar mass

Binary stars
•

Two stars orbiting one another
• Stars are held together by mutual
gravitation
• Both orbit around a common center of mass

24.1 Properties of stars (continued)
 Binary
•

Binary stars
•

•
•

•

stars and stellar mass

Visual binaries are resolved telescopically
More than 50% of the stars in the universe are
binary stars
Used to determine stellar mass

Stellar mass
•

Determined using binary stars – the center of
mass is closest to the most massive star

Binary stars
orbit each
other around
their common
center of
mass
Figure 24.4

24.1 Properties of stars (continued)
 Binary
•

stars and stellar mass

Stellar mass
•

Mass of most stars is between one-tenth and
fifty times the mass of the Sun

24.1 Hertzsprung-Russell
diagram
 Shows
•
•

the relation between stellar

Brightness (absolute magnitude) and
Temperature

 Diagram

is made by plotting (graphing)
each star's
•
•

Luminosity (brightness) and
Temperature

24.1 Hertzsprung-Russell
diagram (continued)
 Parts
•

Main-sequence stars
•

•
•

•

of an H-R diagram

90% of all stars
Band through the center of the H-R diagram
Sun is in the main-sequence

Giants (or red giants)
•
•
•

Very luminous
Large
Upper-right on the H-R diagram

24.1 Hertzsprung-Russell
diagram (continued)
 Parts
•

Giants (or red giants)
•

•

•

of an H-R diagram

Very large giants are called supergiants
Only a few percent of all stars

White dwarfs
•
•

•
•
•

Fainter than main-sequence stars
Small (approximate the size of Earth)
Lower-central area on the H-R diagram
Not all are white in color
Perhaps 10% of all stars

Idealized HertzsprungRussell diagram

Figure 24.5

Quiz Break

24.2 Variable stars
 Stars

that fluctuate in brightness
 Types of variable stars
•

Pulsating variables
•
•

•

Fluctuate regularly in brightness
Expand and contract in size

Eruptive variables
•
•
•

Explosive event
Sudden brightening
Called a nova

24.2 Interstellar matter
 Between

the stars is "the vacuum of

space"
 Nebula
•
•

Cloud of dust and gases
Two major types of nebulae
•

Bright nebula
• Glows if it close to a very hot star
• Two types of bright nebulae
• Emission nebula
• Reflection nebula

The Orion Nebula is a wellknown emission nebula

Figure 24.8

A faint blue reflection nebula in
the Pleiades star cluster

Figure 24.9

24.2 Interstellar matter (continued)
 Nebula
•

Two major types of nebulae
•

Dark nebula
• Not close to any bright star
• Appear dark
• Contains the material that forms stars and
planets

24.2 Stellar evolution
 Stars

exist because of gravity
 Two opposing forces in a star are
•
•

Gravity – contracts
Thermal nuclear energy – expands

 Stages
•

Birth
•

•
•
•
•

In dark, cool, interstellar clouds
Gravity contracts the cloud
Temperature rises
Radiates long-wavelength (red) light
Becomes a protostar

24.2 Stellar evolution (continued)
 Stages
•

Protostar
•
•
•

•
•
•
•

Gravitational contraction of gaseous cloud
continues
Core reaches 10 million K
Hydrogen nuclei fuse
• Become helium nuclei
• Process is called hydrogen burning
Energy is released
Outward pressure increases
Outward pressure balanced by gravity pulling in
Star becomes a stable main-sequence star

24.2 Stellar evolution (continued)
 Stages
•

Main-sequence stage
•

Stars age at different rates
• Massive stars use fuel faster and exist for
only a few million years
• Small stars use fuel slowly and exist for
perhaps hundreds of billions of years

•

90% of a star's life is in the main-sequence

24.2 Stellar evolution (continued)
 Stages
•

Red giant stage
•
•

•
•
•

Hydrogen burning migrates outward
Star's outer envelope expands
• Surface cools
• Surface becomes red
Core is collapsing as helium is converted to
carbon
Eventually all nuclear fuel is used
Gravity squeezes the star

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Low-mass star
• 0.5 solar mass
• Red giant collapses
• Becomes a white dwarf

24.2 Evolutionary stages of
low mass stars

Figure 24.12 A

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Medium-mass star
• Between 0.5 and 3 solar masses
• Red giant collapses
• Planetary nebula forms
• Becomes a white dwarf

24.2 Evolutionary stages of
medium mass stars

Figure 24.12 B

H-R diagram showing
stellar evolution

Figure 24.11

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Massive star
• Over 3 solar masses
• Short life span
• Terminates in a brilliant explosion called
a supernova
• Interior condenses
• May produce a hot, dense object that is
either a neutron star or a black hole

24.2 Evolutionary stages of
massive stars

Figure 24.12 C

24.2 Stellar remnants
 White
•
•

Small (some no larger than Earth)
Dense
•
•
•

•
•

dwarf

Can be more massive than the Sun
Spoonful weighs several tons
Atoms take up less space
• Electrons displaced inward
• Called degenerate matter

Hot surface
Cools to become a black dwarf

24.2 Stellar remnants (continued)
 Neutron
•

Forms from a more massive star
•
•

•
•

star

Star has more gravity
Squeezes itself smaller

Remnant of a supernova
Gravitational force collapses atoms
•
•

Electrons combine with protons to produce
neutrons
Small size

24.2 Stellar remnants (continued)
 Neutron
•

Pea size sample
•
•

•
•

star

Weighs 100 million tons
Same density as an atomic nucleus

Strong magnetic field
First one discovered in early 1970s
•
•

Pulsar (pulsating radio source)
Found in the Crab nebula (remnant of an A.D.
1054 supernova)

Crab Nebula in the
constellation Taurus

Figure 24.14

24.2 Stellar remnants (continued)
 Black
•
•

•

More dense than a neutron star
Intense surface gravity lets no light escape
As matter is pulled into it
•
•

•

hole

Becomes very hot
Emits x-rays

Likely candidate is Cygnus X-1, a strong xray source

Quiz Break

24.3 Galaxies
 Milky
•

Way galaxy

Structure
•
•

•
•

Determined by using radio telescopes
Large spiral galaxy
• About 100,000 light-years wide
• Thickness at the galactic nucleus is about
10,000 light-years
Three spiral arms of stars
Sun is 30,000 light-years from the center

Face-on view of the
Milk Way Galaxy

Figure 24.18 A

Edge-on view of the
Milk Way Galaxy

Figure 24.18 B

24.3 Galaxies (continued)
 Milky
•

Rotation
•
•
•

•

Way galaxy

Around the galactic nucleus
Outermost stars move the slowest
Sun rotates around the galactic nucleus once
about every 200 million years

Halo surrounds the galactic disk
•
•
•

Spherical
Very tenuous gas
Numerous globular clusters

24.3 Galaxies (continued)
 Other
•
•

galaxies

Existence was first proposed in mid-1700s
by Immanuel Kant
Four basic types of galaxies
•

Spiral galaxy
• Arms extending from nucleus
• About 30% of all galaxies
• Large diameter of 20,000 to 125,000 light
years
• Contains both young and old stars
• e.g., Milky Way

Great Galaxy, a spiral galaxy, in
the constellation Andromeda

Figure 24.20

24.3 Galaxies (continued)
 Other
•

galaxies

Four basic types of galaxies
•

•

Barred spiral galaxy
• Stars arranged in the shape of a bar
• Generally quite large
• About 10% of all galaxies
Elliptical galaxy
• Ellipsoidal shape
• About 60% of all galaxies
• Most are smaller than spiral galaxies;
however, they are also the largest known
galaxies

A barred spiral galaxy

Figure 24.22

24.3 Galaxies (continued)
 Other
•

galaxies

Four basic types of galaxies
•

Irregular galaxy
• Lacks symmetry
• About 10% of all galaxies
• Contains mostly young stars
• e.g., Magellanic Clouds

24.3 Galaxies (continued)
 Galactic
•
•
•

Group of galaxies
Some contain thousands of galaxies
Local Group
•
•

•

cluster

Our own group of galaxies
Contains at least 28 galaxies

Supercluster
•
•

Huge swarm of galaxies
May be the largest entity in the universe

Quiz Break

24.4 Red shifts
 Doppler
•

effect

Change in the wavelength of light emitted
by an object due to its motion
•

•

Movement away stretches the wavelength
• Longer wavelength
• Light appears redder
Movement toward “squeezes” the wavelength
• Shorter wavelength
• Light shifted toward the blue

24.4 Red shifts (continued)
 Doppler
•

effect

Amount of the Doppler shift indicates the
rate of movement
•
•

Large Doppler shift indicates a high velocity
Small Doppler shift indicates a lower velocity

 Expanding
•

universe

Most galaxies exhibit a red Doppler shift
•

Moving away

Raisin bread analogy of an
expanding universe

Figure 24.24

24.4 Red shifts (continued)
 Expanding
•

universe

Most galaxies exhibit a red Doppler shift
•

•
•
•

Far galaxies
• Exhibit the greatest shift
• Greater velocity
Discovered in 1929 by Edwin Hubble
Hubble's Law – the recessional speed of
galaxies is proportional to their distance
Accounts for red shifts

24.4 Big Bang theory
 Accounts

for galaxies moving away

from us
 Universe was once confined to a "ball"
that was
•
•

•

Supermassive
Dense
Hot

24.4 Big Bang theory (continued)
 Big

Bang marks the inception of the
universe
•
•

Occurred about 15 billion years ago
All matter and space was created

 Matter

is moving outward
 Fate of the universe
•

Two possibilities
•
•

Universe will last forever
Outward expansion sill stop and gravitational;
contraction will follow

24.4 Big Bang theory (continued)
 Fate
•

of the universe

Final fate depends on the average density
of the universe
•
•

If the density is more than the critical density,
then the universe would contract
Current estimates point to less then the critical
density and predict an ever-expanding, or
open, universe

Chapter 24Test Guidance
You will be responsible on the test for answering 3 of the following 6
questions.
1.

2.

3.
4.
5.
6.

What causes the difference between a star’s apparent
magnitude and it absolute magnitude.
List and explain the three factors that control the apparent
brightness of a star as seen from Earth.
Describe how binary stars are used to determine stellar mass.
List and describe the four basic types of galaxies.
What is Hubble’s Law, please explain in detail.
Briefly describe the Big Bang Theory (not the TV show).

End of Chapter 24


Slide 23

Lecture Outlines
PowerPoint

Chapter 24
Earth Science 11e
Tarbuck/Lutgens
Modified for educational
purposes only
By S. Koziol 12-8-2010

© 2006 Pearson Prentice Hall

Earth Science, 11e
Beyond Our
Solar System
Chapter 24

24.1 Properties of stars
 Distance
•
•

Measuring a star's distance can be very
difficult
Stellar parallax
•
•
•

•
•

Used for measuring distance to a star
Apparent shift in a star's position due to the
orbital motion of Earth
Measured as an angle
Near stars have the largest parallax
Largest parallax is less than one second of arc

24. 1 Properties of stars
(continued)

 Distance
•
•

Distances to the stars are very large
Units of measurement
•
•

•

Kilometers or astronomical units are too
cumbersome to use
Light-year is used most often
• Distance that light travels in 1 year
• One light-year is 9.5 trillion km (5.8 trillion
miles)

Other methods for measuring distance are
also used

24. 1 Properties of stars
(continued)

 Stellar
•

Controlled by three factors
•

•
•

•

brightness

Size
Temperature
Distance

Magnitude
•

Measure of a star's brightness

24.1 Properties of stars
(continued)

 Stellar
•

brightness

Magnitude
•

Two types of measurement
• Apparent magnitude
• Brightness when a star is viewed from
Earth
• Decreases with distance
• Numbers are used to designate
magnitudes - dim stars have large
numbers and negative numbers are also
used

24.1 Properties of stars
(continued)

 Stellar
•

brightness

Magnitude
•

Two types of measurement
• Absolute magnitude
• "True" or intrinsic brightness of a star
• Brightness at a standard distance of
32.6 light-years
• Most stars' absolute magnitudes are
between -5 and +15

24.1 Properties of stars
(continued)

 Color
•

Hot star
•

•
•

•

and temperature

Temperature above 30,000 K
Emits short-wavelength light
Appears blue

Cool star
•
•
•

Temperature less than 3000 K
Emits longer-wavelength light
Appears red

24.1 Properties of stars
(continued)

 Color
•

and temperature

Between 5000 and 6000 K
•
•

Stars appear yellow
e.g., Sun

 Binary
•

stars and stellar mass

Binary stars
•

Two stars orbiting one another
• Stars are held together by mutual
gravitation
• Both orbit around a common center of mass

24.1 Properties of stars (continued)
 Binary
•

Binary stars
•

•
•

•

stars and stellar mass

Visual binaries are resolved telescopically
More than 50% of the stars in the universe are
binary stars
Used to determine stellar mass

Stellar mass
•

Determined using binary stars – the center of
mass is closest to the most massive star

Binary stars
orbit each
other around
their common
center of
mass
Figure 24.4

24.1 Properties of stars (continued)
 Binary
•

stars and stellar mass

Stellar mass
•

Mass of most stars is between one-tenth and
fifty times the mass of the Sun

24.1 Hertzsprung-Russell
diagram
 Shows
•
•

the relation between stellar

Brightness (absolute magnitude) and
Temperature

 Diagram

is made by plotting (graphing)
each star's
•
•

Luminosity (brightness) and
Temperature

24.1 Hertzsprung-Russell
diagram (continued)
 Parts
•

Main-sequence stars
•

•
•

•

of an H-R diagram

90% of all stars
Band through the center of the H-R diagram
Sun is in the main-sequence

Giants (or red giants)
•
•
•

Very luminous
Large
Upper-right on the H-R diagram

24.1 Hertzsprung-Russell
diagram (continued)
 Parts
•

Giants (or red giants)
•

•

•

of an H-R diagram

Very large giants are called supergiants
Only a few percent of all stars

White dwarfs
•
•

•
•
•

Fainter than main-sequence stars
Small (approximate the size of Earth)
Lower-central area on the H-R diagram
Not all are white in color
Perhaps 10% of all stars

Idealized HertzsprungRussell diagram

Figure 24.5

Quiz Break

24.2 Variable stars
 Stars

that fluctuate in brightness
 Types of variable stars
•

Pulsating variables
•
•

•

Fluctuate regularly in brightness
Expand and contract in size

Eruptive variables
•
•
•

Explosive event
Sudden brightening
Called a nova

24.2 Interstellar matter
 Between

the stars is "the vacuum of

space"
 Nebula
•
•

Cloud of dust and gases
Two major types of nebulae
•

Bright nebula
• Glows if it close to a very hot star
• Two types of bright nebulae
• Emission nebula
• Reflection nebula

The Orion Nebula is a wellknown emission nebula

Figure 24.8

A faint blue reflection nebula in
the Pleiades star cluster

Figure 24.9

24.2 Interstellar matter (continued)
 Nebula
•

Two major types of nebulae
•

Dark nebula
• Not close to any bright star
• Appear dark
• Contains the material that forms stars and
planets

24.2 Stellar evolution
 Stars

exist because of gravity
 Two opposing forces in a star are
•
•

Gravity – contracts
Thermal nuclear energy – expands

 Stages
•

Birth
•

•
•
•
•

In dark, cool, interstellar clouds
Gravity contracts the cloud
Temperature rises
Radiates long-wavelength (red) light
Becomes a protostar

24.2 Stellar evolution (continued)
 Stages
•

Protostar
•
•
•

•
•
•
•

Gravitational contraction of gaseous cloud
continues
Core reaches 10 million K
Hydrogen nuclei fuse
• Become helium nuclei
• Process is called hydrogen burning
Energy is released
Outward pressure increases
Outward pressure balanced by gravity pulling in
Star becomes a stable main-sequence star

24.2 Stellar evolution (continued)
 Stages
•

Main-sequence stage
•

Stars age at different rates
• Massive stars use fuel faster and exist for
only a few million years
• Small stars use fuel slowly and exist for
perhaps hundreds of billions of years

•

90% of a star's life is in the main-sequence

24.2 Stellar evolution (continued)
 Stages
•

Red giant stage
•
•

•
•
•

Hydrogen burning migrates outward
Star's outer envelope expands
• Surface cools
• Surface becomes red
Core is collapsing as helium is converted to
carbon
Eventually all nuclear fuel is used
Gravity squeezes the star

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Low-mass star
• 0.5 solar mass
• Red giant collapses
• Becomes a white dwarf

24.2 Evolutionary stages of
low mass stars

Figure 24.12 A

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Medium-mass star
• Between 0.5 and 3 solar masses
• Red giant collapses
• Planetary nebula forms
• Becomes a white dwarf

24.2 Evolutionary stages of
medium mass stars

Figure 24.12 B

H-R diagram showing
stellar evolution

Figure 24.11

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Massive star
• Over 3 solar masses
• Short life span
• Terminates in a brilliant explosion called
a supernova
• Interior condenses
• May produce a hot, dense object that is
either a neutron star or a black hole

24.2 Evolutionary stages of
massive stars

Figure 24.12 C

24.2 Stellar remnants
 White
•
•

Small (some no larger than Earth)
Dense
•
•
•

•
•

dwarf

Can be more massive than the Sun
Spoonful weighs several tons
Atoms take up less space
• Electrons displaced inward
• Called degenerate matter

Hot surface
Cools to become a black dwarf

24.2 Stellar remnants (continued)
 Neutron
•

Forms from a more massive star
•
•

•
•

star

Star has more gravity
Squeezes itself smaller

Remnant of a supernova
Gravitational force collapses atoms
•
•

Electrons combine with protons to produce
neutrons
Small size

24.2 Stellar remnants (continued)
 Neutron
•

Pea size sample
•
•

•
•

star

Weighs 100 million tons
Same density as an atomic nucleus

Strong magnetic field
First one discovered in early 1970s
•
•

Pulsar (pulsating radio source)
Found in the Crab nebula (remnant of an A.D.
1054 supernova)

Crab Nebula in the
constellation Taurus

Figure 24.14

24.2 Stellar remnants (continued)
 Black
•
•

•

More dense than a neutron star
Intense surface gravity lets no light escape
As matter is pulled into it
•
•

•

hole

Becomes very hot
Emits x-rays

Likely candidate is Cygnus X-1, a strong xray source

Quiz Break

24.3 Galaxies
 Milky
•

Way galaxy

Structure
•
•

•
•

Determined by using radio telescopes
Large spiral galaxy
• About 100,000 light-years wide
• Thickness at the galactic nucleus is about
10,000 light-years
Three spiral arms of stars
Sun is 30,000 light-years from the center

Face-on view of the
Milk Way Galaxy

Figure 24.18 A

Edge-on view of the
Milk Way Galaxy

Figure 24.18 B

24.3 Galaxies (continued)
 Milky
•

Rotation
•
•
•

•

Way galaxy

Around the galactic nucleus
Outermost stars move the slowest
Sun rotates around the galactic nucleus once
about every 200 million years

Halo surrounds the galactic disk
•
•
•

Spherical
Very tenuous gas
Numerous globular clusters

24.3 Galaxies (continued)
 Other
•
•

galaxies

Existence was first proposed in mid-1700s
by Immanuel Kant
Four basic types of galaxies
•

Spiral galaxy
• Arms extending from nucleus
• About 30% of all galaxies
• Large diameter of 20,000 to 125,000 light
years
• Contains both young and old stars
• e.g., Milky Way

Great Galaxy, a spiral galaxy, in
the constellation Andromeda

Figure 24.20

24.3 Galaxies (continued)
 Other
•

galaxies

Four basic types of galaxies
•

•

Barred spiral galaxy
• Stars arranged in the shape of a bar
• Generally quite large
• About 10% of all galaxies
Elliptical galaxy
• Ellipsoidal shape
• About 60% of all galaxies
• Most are smaller than spiral galaxies;
however, they are also the largest known
galaxies

A barred spiral galaxy

Figure 24.22

24.3 Galaxies (continued)
 Other
•

galaxies

Four basic types of galaxies
•

Irregular galaxy
• Lacks symmetry
• About 10% of all galaxies
• Contains mostly young stars
• e.g., Magellanic Clouds

24.3 Galaxies (continued)
 Galactic
•
•
•

Group of galaxies
Some contain thousands of galaxies
Local Group
•
•

•

cluster

Our own group of galaxies
Contains at least 28 galaxies

Supercluster
•
•

Huge swarm of galaxies
May be the largest entity in the universe

Quiz Break

24.4 Red shifts
 Doppler
•

effect

Change in the wavelength of light emitted
by an object due to its motion
•

•

Movement away stretches the wavelength
• Longer wavelength
• Light appears redder
Movement toward “squeezes” the wavelength
• Shorter wavelength
• Light shifted toward the blue

24.4 Red shifts (continued)
 Doppler
•

effect

Amount of the Doppler shift indicates the
rate of movement
•
•

Large Doppler shift indicates a high velocity
Small Doppler shift indicates a lower velocity

 Expanding
•

universe

Most galaxies exhibit a red Doppler shift
•

Moving away

Raisin bread analogy of an
expanding universe

Figure 24.24

24.4 Red shifts (continued)
 Expanding
•

universe

Most galaxies exhibit a red Doppler shift
•

•
•
•

Far galaxies
• Exhibit the greatest shift
• Greater velocity
Discovered in 1929 by Edwin Hubble
Hubble's Law – the recessional speed of
galaxies is proportional to their distance
Accounts for red shifts

24.4 Big Bang theory
 Accounts

for galaxies moving away

from us
 Universe was once confined to a "ball"
that was
•
•

•

Supermassive
Dense
Hot

24.4 Big Bang theory (continued)
 Big

Bang marks the inception of the
universe
•
•

Occurred about 15 billion years ago
All matter and space was created

 Matter

is moving outward
 Fate of the universe
•

Two possibilities
•
•

Universe will last forever
Outward expansion sill stop and gravitational;
contraction will follow

24.4 Big Bang theory (continued)
 Fate
•

of the universe

Final fate depends on the average density
of the universe
•
•

If the density is more than the critical density,
then the universe would contract
Current estimates point to less then the critical
density and predict an ever-expanding, or
open, universe

Chapter 24Test Guidance
You will be responsible on the test for answering 3 of the following 6
questions.
1.

2.

3.
4.
5.
6.

What causes the difference between a star’s apparent
magnitude and it absolute magnitude.
List and explain the three factors that control the apparent
brightness of a star as seen from Earth.
Describe how binary stars are used to determine stellar mass.
List and describe the four basic types of galaxies.
What is Hubble’s Law, please explain in detail.
Briefly describe the Big Bang Theory (not the TV show).

End of Chapter 24


Slide 24

Lecture Outlines
PowerPoint

Chapter 24
Earth Science 11e
Tarbuck/Lutgens
Modified for educational
purposes only
By S. Koziol 12-8-2010

© 2006 Pearson Prentice Hall

Earth Science, 11e
Beyond Our
Solar System
Chapter 24

24.1 Properties of stars
 Distance
•
•

Measuring a star's distance can be very
difficult
Stellar parallax
•
•
•

•
•

Used for measuring distance to a star
Apparent shift in a star's position due to the
orbital motion of Earth
Measured as an angle
Near stars have the largest parallax
Largest parallax is less than one second of arc

24. 1 Properties of stars
(continued)

 Distance
•
•

Distances to the stars are very large
Units of measurement
•
•

•

Kilometers or astronomical units are too
cumbersome to use
Light-year is used most often
• Distance that light travels in 1 year
• One light-year is 9.5 trillion km (5.8 trillion
miles)

Other methods for measuring distance are
also used

24. 1 Properties of stars
(continued)

 Stellar
•

Controlled by three factors
•

•
•

•

brightness

Size
Temperature
Distance

Magnitude
•

Measure of a star's brightness

24.1 Properties of stars
(continued)

 Stellar
•

brightness

Magnitude
•

Two types of measurement
• Apparent magnitude
• Brightness when a star is viewed from
Earth
• Decreases with distance
• Numbers are used to designate
magnitudes - dim stars have large
numbers and negative numbers are also
used

24.1 Properties of stars
(continued)

 Stellar
•

brightness

Magnitude
•

Two types of measurement
• Absolute magnitude
• "True" or intrinsic brightness of a star
• Brightness at a standard distance of
32.6 light-years
• Most stars' absolute magnitudes are
between -5 and +15

24.1 Properties of stars
(continued)

 Color
•

Hot star
•

•
•

•

and temperature

Temperature above 30,000 K
Emits short-wavelength light
Appears blue

Cool star
•
•
•

Temperature less than 3000 K
Emits longer-wavelength light
Appears red

24.1 Properties of stars
(continued)

 Color
•

and temperature

Between 5000 and 6000 K
•
•

Stars appear yellow
e.g., Sun

 Binary
•

stars and stellar mass

Binary stars
•

Two stars orbiting one another
• Stars are held together by mutual
gravitation
• Both orbit around a common center of mass

24.1 Properties of stars (continued)
 Binary
•

Binary stars
•

•
•

•

stars and stellar mass

Visual binaries are resolved telescopically
More than 50% of the stars in the universe are
binary stars
Used to determine stellar mass

Stellar mass
•

Determined using binary stars – the center of
mass is closest to the most massive star

Binary stars
orbit each
other around
their common
center of
mass
Figure 24.4

24.1 Properties of stars (continued)
 Binary
•

stars and stellar mass

Stellar mass
•

Mass of most stars is between one-tenth and
fifty times the mass of the Sun

24.1 Hertzsprung-Russell
diagram
 Shows
•
•

the relation between stellar

Brightness (absolute magnitude) and
Temperature

 Diagram

is made by plotting (graphing)
each star's
•
•

Luminosity (brightness) and
Temperature

24.1 Hertzsprung-Russell
diagram (continued)
 Parts
•

Main-sequence stars
•

•
•

•

of an H-R diagram

90% of all stars
Band through the center of the H-R diagram
Sun is in the main-sequence

Giants (or red giants)
•
•
•

Very luminous
Large
Upper-right on the H-R diagram

24.1 Hertzsprung-Russell
diagram (continued)
 Parts
•

Giants (or red giants)
•

•

•

of an H-R diagram

Very large giants are called supergiants
Only a few percent of all stars

White dwarfs
•
•

•
•
•

Fainter than main-sequence stars
Small (approximate the size of Earth)
Lower-central area on the H-R diagram
Not all are white in color
Perhaps 10% of all stars

Idealized HertzsprungRussell diagram

Figure 24.5

Quiz Break

24.2 Variable stars
 Stars

that fluctuate in brightness
 Types of variable stars
•

Pulsating variables
•
•

•

Fluctuate regularly in brightness
Expand and contract in size

Eruptive variables
•
•
•

Explosive event
Sudden brightening
Called a nova

24.2 Interstellar matter
 Between

the stars is "the vacuum of

space"
 Nebula
•
•

Cloud of dust and gases
Two major types of nebulae
•

Bright nebula
• Glows if it close to a very hot star
• Two types of bright nebulae
• Emission nebula
• Reflection nebula

The Orion Nebula is a wellknown emission nebula

Figure 24.8

A faint blue reflection nebula in
the Pleiades star cluster

Figure 24.9

24.2 Interstellar matter (continued)
 Nebula
•

Two major types of nebulae
•

Dark nebula
• Not close to any bright star
• Appear dark
• Contains the material that forms stars and
planets

24.2 Stellar evolution
 Stars

exist because of gravity
 Two opposing forces in a star are
•
•

Gravity – contracts
Thermal nuclear energy – expands

 Stages
•

Birth
•

•
•
•
•

In dark, cool, interstellar clouds
Gravity contracts the cloud
Temperature rises
Radiates long-wavelength (red) light
Becomes a protostar

24.2 Stellar evolution (continued)
 Stages
•

Protostar
•
•
•

•
•
•
•

Gravitational contraction of gaseous cloud
continues
Core reaches 10 million K
Hydrogen nuclei fuse
• Become helium nuclei
• Process is called hydrogen burning
Energy is released
Outward pressure increases
Outward pressure balanced by gravity pulling in
Star becomes a stable main-sequence star

24.2 Stellar evolution (continued)
 Stages
•

Main-sequence stage
•

Stars age at different rates
• Massive stars use fuel faster and exist for
only a few million years
• Small stars use fuel slowly and exist for
perhaps hundreds of billions of years

•

90% of a star's life is in the main-sequence

24.2 Stellar evolution (continued)
 Stages
•

Red giant stage
•
•

•
•
•

Hydrogen burning migrates outward
Star's outer envelope expands
• Surface cools
• Surface becomes red
Core is collapsing as helium is converted to
carbon
Eventually all nuclear fuel is used
Gravity squeezes the star

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Low-mass star
• 0.5 solar mass
• Red giant collapses
• Becomes a white dwarf

24.2 Evolutionary stages of
low mass stars

Figure 24.12 A

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Medium-mass star
• Between 0.5 and 3 solar masses
• Red giant collapses
• Planetary nebula forms
• Becomes a white dwarf

24.2 Evolutionary stages of
medium mass stars

Figure 24.12 B

H-R diagram showing
stellar evolution

Figure 24.11

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Massive star
• Over 3 solar masses
• Short life span
• Terminates in a brilliant explosion called
a supernova
• Interior condenses
• May produce a hot, dense object that is
either a neutron star or a black hole

24.2 Evolutionary stages of
massive stars

Figure 24.12 C

24.2 Stellar remnants
 White
•
•

Small (some no larger than Earth)
Dense
•
•
•

•
•

dwarf

Can be more massive than the Sun
Spoonful weighs several tons
Atoms take up less space
• Electrons displaced inward
• Called degenerate matter

Hot surface
Cools to become a black dwarf

24.2 Stellar remnants (continued)
 Neutron
•

Forms from a more massive star
•
•

•
•

star

Star has more gravity
Squeezes itself smaller

Remnant of a supernova
Gravitational force collapses atoms
•
•

Electrons combine with protons to produce
neutrons
Small size

24.2 Stellar remnants (continued)
 Neutron
•

Pea size sample
•
•

•
•

star

Weighs 100 million tons
Same density as an atomic nucleus

Strong magnetic field
First one discovered in early 1970s
•
•

Pulsar (pulsating radio source)
Found in the Crab nebula (remnant of an A.D.
1054 supernova)

Crab Nebula in the
constellation Taurus

Figure 24.14

24.2 Stellar remnants (continued)
 Black
•
•

•

More dense than a neutron star
Intense surface gravity lets no light escape
As matter is pulled into it
•
•

•

hole

Becomes very hot
Emits x-rays

Likely candidate is Cygnus X-1, a strong xray source

Quiz Break

24.3 Galaxies
 Milky
•

Way galaxy

Structure
•
•

•
•

Determined by using radio telescopes
Large spiral galaxy
• About 100,000 light-years wide
• Thickness at the galactic nucleus is about
10,000 light-years
Three spiral arms of stars
Sun is 30,000 light-years from the center

Face-on view of the
Milk Way Galaxy

Figure 24.18 A

Edge-on view of the
Milk Way Galaxy

Figure 24.18 B

24.3 Galaxies (continued)
 Milky
•

Rotation
•
•
•

•

Way galaxy

Around the galactic nucleus
Outermost stars move the slowest
Sun rotates around the galactic nucleus once
about every 200 million years

Halo surrounds the galactic disk
•
•
•

Spherical
Very tenuous gas
Numerous globular clusters

24.3 Galaxies (continued)
 Other
•
•

galaxies

Existence was first proposed in mid-1700s
by Immanuel Kant
Four basic types of galaxies
•

Spiral galaxy
• Arms extending from nucleus
• About 30% of all galaxies
• Large diameter of 20,000 to 125,000 light
years
• Contains both young and old stars
• e.g., Milky Way

Great Galaxy, a spiral galaxy, in
the constellation Andromeda

Figure 24.20

24.3 Galaxies (continued)
 Other
•

galaxies

Four basic types of galaxies
•

•

Barred spiral galaxy
• Stars arranged in the shape of a bar
• Generally quite large
• About 10% of all galaxies
Elliptical galaxy
• Ellipsoidal shape
• About 60% of all galaxies
• Most are smaller than spiral galaxies;
however, they are also the largest known
galaxies

A barred spiral galaxy

Figure 24.22

24.3 Galaxies (continued)
 Other
•

galaxies

Four basic types of galaxies
•

Irregular galaxy
• Lacks symmetry
• About 10% of all galaxies
• Contains mostly young stars
• e.g., Magellanic Clouds

24.3 Galaxies (continued)
 Galactic
•
•
•

Group of galaxies
Some contain thousands of galaxies
Local Group
•
•

•

cluster

Our own group of galaxies
Contains at least 28 galaxies

Supercluster
•
•

Huge swarm of galaxies
May be the largest entity in the universe

Quiz Break

24.4 Red shifts
 Doppler
•

effect

Change in the wavelength of light emitted
by an object due to its motion
•

•

Movement away stretches the wavelength
• Longer wavelength
• Light appears redder
Movement toward “squeezes” the wavelength
• Shorter wavelength
• Light shifted toward the blue

24.4 Red shifts (continued)
 Doppler
•

effect

Amount of the Doppler shift indicates the
rate of movement
•
•

Large Doppler shift indicates a high velocity
Small Doppler shift indicates a lower velocity

 Expanding
•

universe

Most galaxies exhibit a red Doppler shift
•

Moving away

Raisin bread analogy of an
expanding universe

Figure 24.24

24.4 Red shifts (continued)
 Expanding
•

universe

Most galaxies exhibit a red Doppler shift
•

•
•
•

Far galaxies
• Exhibit the greatest shift
• Greater velocity
Discovered in 1929 by Edwin Hubble
Hubble's Law – the recessional speed of
galaxies is proportional to their distance
Accounts for red shifts

24.4 Big Bang theory
 Accounts

for galaxies moving away

from us
 Universe was once confined to a "ball"
that was
•
•

•

Supermassive
Dense
Hot

24.4 Big Bang theory (continued)
 Big

Bang marks the inception of the
universe
•
•

Occurred about 15 billion years ago
All matter and space was created

 Matter

is moving outward
 Fate of the universe
•

Two possibilities
•
•

Universe will last forever
Outward expansion sill stop and gravitational;
contraction will follow

24.4 Big Bang theory (continued)
 Fate
•

of the universe

Final fate depends on the average density
of the universe
•
•

If the density is more than the critical density,
then the universe would contract
Current estimates point to less then the critical
density and predict an ever-expanding, or
open, universe

Chapter 24Test Guidance
You will be responsible on the test for answering 3 of the following 6
questions.
1.

2.

3.
4.
5.
6.

What causes the difference between a star’s apparent
magnitude and it absolute magnitude.
List and explain the three factors that control the apparent
brightness of a star as seen from Earth.
Describe how binary stars are used to determine stellar mass.
List and describe the four basic types of galaxies.
What is Hubble’s Law, please explain in detail.
Briefly describe the Big Bang Theory (not the TV show).

End of Chapter 24


Slide 25

Lecture Outlines
PowerPoint

Chapter 24
Earth Science 11e
Tarbuck/Lutgens
Modified for educational
purposes only
By S. Koziol 12-8-2010

© 2006 Pearson Prentice Hall

Earth Science, 11e
Beyond Our
Solar System
Chapter 24

24.1 Properties of stars
 Distance
•
•

Measuring a star's distance can be very
difficult
Stellar parallax
•
•
•

•
•

Used for measuring distance to a star
Apparent shift in a star's position due to the
orbital motion of Earth
Measured as an angle
Near stars have the largest parallax
Largest parallax is less than one second of arc

24. 1 Properties of stars
(continued)

 Distance
•
•

Distances to the stars are very large
Units of measurement
•
•

•

Kilometers or astronomical units are too
cumbersome to use
Light-year is used most often
• Distance that light travels in 1 year
• One light-year is 9.5 trillion km (5.8 trillion
miles)

Other methods for measuring distance are
also used

24. 1 Properties of stars
(continued)

 Stellar
•

Controlled by three factors
•

•
•

•

brightness

Size
Temperature
Distance

Magnitude
•

Measure of a star's brightness

24.1 Properties of stars
(continued)

 Stellar
•

brightness

Magnitude
•

Two types of measurement
• Apparent magnitude
• Brightness when a star is viewed from
Earth
• Decreases with distance
• Numbers are used to designate
magnitudes - dim stars have large
numbers and negative numbers are also
used

24.1 Properties of stars
(continued)

 Stellar
•

brightness

Magnitude
•

Two types of measurement
• Absolute magnitude
• "True" or intrinsic brightness of a star
• Brightness at a standard distance of
32.6 light-years
• Most stars' absolute magnitudes are
between -5 and +15

24.1 Properties of stars
(continued)

 Color
•

Hot star
•

•
•

•

and temperature

Temperature above 30,000 K
Emits short-wavelength light
Appears blue

Cool star
•
•
•

Temperature less than 3000 K
Emits longer-wavelength light
Appears red

24.1 Properties of stars
(continued)

 Color
•

and temperature

Between 5000 and 6000 K
•
•

Stars appear yellow
e.g., Sun

 Binary
•

stars and stellar mass

Binary stars
•

Two stars orbiting one another
• Stars are held together by mutual
gravitation
• Both orbit around a common center of mass

24.1 Properties of stars (continued)
 Binary
•

Binary stars
•

•
•

•

stars and stellar mass

Visual binaries are resolved telescopically
More than 50% of the stars in the universe are
binary stars
Used to determine stellar mass

Stellar mass
•

Determined using binary stars – the center of
mass is closest to the most massive star

Binary stars
orbit each
other around
their common
center of
mass
Figure 24.4

24.1 Properties of stars (continued)
 Binary
•

stars and stellar mass

Stellar mass
•

Mass of most stars is between one-tenth and
fifty times the mass of the Sun

24.1 Hertzsprung-Russell
diagram
 Shows
•
•

the relation between stellar

Brightness (absolute magnitude) and
Temperature

 Diagram

is made by plotting (graphing)
each star's
•
•

Luminosity (brightness) and
Temperature

24.1 Hertzsprung-Russell
diagram (continued)
 Parts
•

Main-sequence stars
•

•
•

•

of an H-R diagram

90% of all stars
Band through the center of the H-R diagram
Sun is in the main-sequence

Giants (or red giants)
•
•
•

Very luminous
Large
Upper-right on the H-R diagram

24.1 Hertzsprung-Russell
diagram (continued)
 Parts
•

Giants (or red giants)
•

•

•

of an H-R diagram

Very large giants are called supergiants
Only a few percent of all stars

White dwarfs
•
•

•
•
•

Fainter than main-sequence stars
Small (approximate the size of Earth)
Lower-central area on the H-R diagram
Not all are white in color
Perhaps 10% of all stars

Idealized HertzsprungRussell diagram

Figure 24.5

Quiz Break

24.2 Variable stars
 Stars

that fluctuate in brightness
 Types of variable stars
•

Pulsating variables
•
•

•

Fluctuate regularly in brightness
Expand and contract in size

Eruptive variables
•
•
•

Explosive event
Sudden brightening
Called a nova

24.2 Interstellar matter
 Between

the stars is "the vacuum of

space"
 Nebula
•
•

Cloud of dust and gases
Two major types of nebulae
•

Bright nebula
• Glows if it close to a very hot star
• Two types of bright nebulae
• Emission nebula
• Reflection nebula

The Orion Nebula is a wellknown emission nebula

Figure 24.8

A faint blue reflection nebula in
the Pleiades star cluster

Figure 24.9

24.2 Interstellar matter (continued)
 Nebula
•

Two major types of nebulae
•

Dark nebula
• Not close to any bright star
• Appear dark
• Contains the material that forms stars and
planets

24.2 Stellar evolution
 Stars

exist because of gravity
 Two opposing forces in a star are
•
•

Gravity – contracts
Thermal nuclear energy – expands

 Stages
•

Birth
•

•
•
•
•

In dark, cool, interstellar clouds
Gravity contracts the cloud
Temperature rises
Radiates long-wavelength (red) light
Becomes a protostar

24.2 Stellar evolution (continued)
 Stages
•

Protostar
•
•
•

•
•
•
•

Gravitational contraction of gaseous cloud
continues
Core reaches 10 million K
Hydrogen nuclei fuse
• Become helium nuclei
• Process is called hydrogen burning
Energy is released
Outward pressure increases
Outward pressure balanced by gravity pulling in
Star becomes a stable main-sequence star

24.2 Stellar evolution (continued)
 Stages
•

Main-sequence stage
•

Stars age at different rates
• Massive stars use fuel faster and exist for
only a few million years
• Small stars use fuel slowly and exist for
perhaps hundreds of billions of years

•

90% of a star's life is in the main-sequence

24.2 Stellar evolution (continued)
 Stages
•

Red giant stage
•
•

•
•
•

Hydrogen burning migrates outward
Star's outer envelope expands
• Surface cools
• Surface becomes red
Core is collapsing as helium is converted to
carbon
Eventually all nuclear fuel is used
Gravity squeezes the star

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Low-mass star
• 0.5 solar mass
• Red giant collapses
• Becomes a white dwarf

24.2 Evolutionary stages of
low mass stars

Figure 24.12 A

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Medium-mass star
• Between 0.5 and 3 solar masses
• Red giant collapses
• Planetary nebula forms
• Becomes a white dwarf

24.2 Evolutionary stages of
medium mass stars

Figure 24.12 B

H-R diagram showing
stellar evolution

Figure 24.11

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Massive star
• Over 3 solar masses
• Short life span
• Terminates in a brilliant explosion called
a supernova
• Interior condenses
• May produce a hot, dense object that is
either a neutron star or a black hole

24.2 Evolutionary stages of
massive stars

Figure 24.12 C

24.2 Stellar remnants
 White
•
•

Small (some no larger than Earth)
Dense
•
•
•

•
•

dwarf

Can be more massive than the Sun
Spoonful weighs several tons
Atoms take up less space
• Electrons displaced inward
• Called degenerate matter

Hot surface
Cools to become a black dwarf

24.2 Stellar remnants (continued)
 Neutron
•

Forms from a more massive star
•
•

•
•

star

Star has more gravity
Squeezes itself smaller

Remnant of a supernova
Gravitational force collapses atoms
•
•

Electrons combine with protons to produce
neutrons
Small size

24.2 Stellar remnants (continued)
 Neutron
•

Pea size sample
•
•

•
•

star

Weighs 100 million tons
Same density as an atomic nucleus

Strong magnetic field
First one discovered in early 1970s
•
•

Pulsar (pulsating radio source)
Found in the Crab nebula (remnant of an A.D.
1054 supernova)

Crab Nebula in the
constellation Taurus

Figure 24.14

24.2 Stellar remnants (continued)
 Black
•
•

•

More dense than a neutron star
Intense surface gravity lets no light escape
As matter is pulled into it
•
•

•

hole

Becomes very hot
Emits x-rays

Likely candidate is Cygnus X-1, a strong xray source

Quiz Break

24.3 Galaxies
 Milky
•

Way galaxy

Structure
•
•

•
•

Determined by using radio telescopes
Large spiral galaxy
• About 100,000 light-years wide
• Thickness at the galactic nucleus is about
10,000 light-years
Three spiral arms of stars
Sun is 30,000 light-years from the center

Face-on view of the
Milk Way Galaxy

Figure 24.18 A

Edge-on view of the
Milk Way Galaxy

Figure 24.18 B

24.3 Galaxies (continued)
 Milky
•

Rotation
•
•
•

•

Way galaxy

Around the galactic nucleus
Outermost stars move the slowest
Sun rotates around the galactic nucleus once
about every 200 million years

Halo surrounds the galactic disk
•
•
•

Spherical
Very tenuous gas
Numerous globular clusters

24.3 Galaxies (continued)
 Other
•
•

galaxies

Existence was first proposed in mid-1700s
by Immanuel Kant
Four basic types of galaxies
•

Spiral galaxy
• Arms extending from nucleus
• About 30% of all galaxies
• Large diameter of 20,000 to 125,000 light
years
• Contains both young and old stars
• e.g., Milky Way

Great Galaxy, a spiral galaxy, in
the constellation Andromeda

Figure 24.20

24.3 Galaxies (continued)
 Other
•

galaxies

Four basic types of galaxies
•

•

Barred spiral galaxy
• Stars arranged in the shape of a bar
• Generally quite large
• About 10% of all galaxies
Elliptical galaxy
• Ellipsoidal shape
• About 60% of all galaxies
• Most are smaller than spiral galaxies;
however, they are also the largest known
galaxies

A barred spiral galaxy

Figure 24.22

24.3 Galaxies (continued)
 Other
•

galaxies

Four basic types of galaxies
•

Irregular galaxy
• Lacks symmetry
• About 10% of all galaxies
• Contains mostly young stars
• e.g., Magellanic Clouds

24.3 Galaxies (continued)
 Galactic
•
•
•

Group of galaxies
Some contain thousands of galaxies
Local Group
•
•

•

cluster

Our own group of galaxies
Contains at least 28 galaxies

Supercluster
•
•

Huge swarm of galaxies
May be the largest entity in the universe

Quiz Break

24.4 Red shifts
 Doppler
•

effect

Change in the wavelength of light emitted
by an object due to its motion
•

•

Movement away stretches the wavelength
• Longer wavelength
• Light appears redder
Movement toward “squeezes” the wavelength
• Shorter wavelength
• Light shifted toward the blue

24.4 Red shifts (continued)
 Doppler
•

effect

Amount of the Doppler shift indicates the
rate of movement
•
•

Large Doppler shift indicates a high velocity
Small Doppler shift indicates a lower velocity

 Expanding
•

universe

Most galaxies exhibit a red Doppler shift
•

Moving away

Raisin bread analogy of an
expanding universe

Figure 24.24

24.4 Red shifts (continued)
 Expanding
•

universe

Most galaxies exhibit a red Doppler shift
•

•
•
•

Far galaxies
• Exhibit the greatest shift
• Greater velocity
Discovered in 1929 by Edwin Hubble
Hubble's Law – the recessional speed of
galaxies is proportional to their distance
Accounts for red shifts

24.4 Big Bang theory
 Accounts

for galaxies moving away

from us
 Universe was once confined to a "ball"
that was
•
•

•

Supermassive
Dense
Hot

24.4 Big Bang theory (continued)
 Big

Bang marks the inception of the
universe
•
•

Occurred about 15 billion years ago
All matter and space was created

 Matter

is moving outward
 Fate of the universe
•

Two possibilities
•
•

Universe will last forever
Outward expansion sill stop and gravitational;
contraction will follow

24.4 Big Bang theory (continued)
 Fate
•

of the universe

Final fate depends on the average density
of the universe
•
•

If the density is more than the critical density,
then the universe would contract
Current estimates point to less then the critical
density and predict an ever-expanding, or
open, universe

Chapter 24Test Guidance
You will be responsible on the test for answering 3 of the following 6
questions.
1.

2.

3.
4.
5.
6.

What causes the difference between a star’s apparent
magnitude and it absolute magnitude.
List and explain the three factors that control the apparent
brightness of a star as seen from Earth.
Describe how binary stars are used to determine stellar mass.
List and describe the four basic types of galaxies.
What is Hubble’s Law, please explain in detail.
Briefly describe the Big Bang Theory (not the TV show).

End of Chapter 24


Slide 26

Lecture Outlines
PowerPoint

Chapter 24
Earth Science 11e
Tarbuck/Lutgens
Modified for educational
purposes only
By S. Koziol 12-8-2010

© 2006 Pearson Prentice Hall

Earth Science, 11e
Beyond Our
Solar System
Chapter 24

24.1 Properties of stars
 Distance
•
•

Measuring a star's distance can be very
difficult
Stellar parallax
•
•
•

•
•

Used for measuring distance to a star
Apparent shift in a star's position due to the
orbital motion of Earth
Measured as an angle
Near stars have the largest parallax
Largest parallax is less than one second of arc

24. 1 Properties of stars
(continued)

 Distance
•
•

Distances to the stars are very large
Units of measurement
•
•

•

Kilometers or astronomical units are too
cumbersome to use
Light-year is used most often
• Distance that light travels in 1 year
• One light-year is 9.5 trillion km (5.8 trillion
miles)

Other methods for measuring distance are
also used

24. 1 Properties of stars
(continued)

 Stellar
•

Controlled by three factors
•

•
•

•

brightness

Size
Temperature
Distance

Magnitude
•

Measure of a star's brightness

24.1 Properties of stars
(continued)

 Stellar
•

brightness

Magnitude
•

Two types of measurement
• Apparent magnitude
• Brightness when a star is viewed from
Earth
• Decreases with distance
• Numbers are used to designate
magnitudes - dim stars have large
numbers and negative numbers are also
used

24.1 Properties of stars
(continued)

 Stellar
•

brightness

Magnitude
•

Two types of measurement
• Absolute magnitude
• "True" or intrinsic brightness of a star
• Brightness at a standard distance of
32.6 light-years
• Most stars' absolute magnitudes are
between -5 and +15

24.1 Properties of stars
(continued)

 Color
•

Hot star
•

•
•

•

and temperature

Temperature above 30,000 K
Emits short-wavelength light
Appears blue

Cool star
•
•
•

Temperature less than 3000 K
Emits longer-wavelength light
Appears red

24.1 Properties of stars
(continued)

 Color
•

and temperature

Between 5000 and 6000 K
•
•

Stars appear yellow
e.g., Sun

 Binary
•

stars and stellar mass

Binary stars
•

Two stars orbiting one another
• Stars are held together by mutual
gravitation
• Both orbit around a common center of mass

24.1 Properties of stars (continued)
 Binary
•

Binary stars
•

•
•

•

stars and stellar mass

Visual binaries are resolved telescopically
More than 50% of the stars in the universe are
binary stars
Used to determine stellar mass

Stellar mass
•

Determined using binary stars – the center of
mass is closest to the most massive star

Binary stars
orbit each
other around
their common
center of
mass
Figure 24.4

24.1 Properties of stars (continued)
 Binary
•

stars and stellar mass

Stellar mass
•

Mass of most stars is between one-tenth and
fifty times the mass of the Sun

24.1 Hertzsprung-Russell
diagram
 Shows
•
•

the relation between stellar

Brightness (absolute magnitude) and
Temperature

 Diagram

is made by plotting (graphing)
each star's
•
•

Luminosity (brightness) and
Temperature

24.1 Hertzsprung-Russell
diagram (continued)
 Parts
•

Main-sequence stars
•

•
•

•

of an H-R diagram

90% of all stars
Band through the center of the H-R diagram
Sun is in the main-sequence

Giants (or red giants)
•
•
•

Very luminous
Large
Upper-right on the H-R diagram

24.1 Hertzsprung-Russell
diagram (continued)
 Parts
•

Giants (or red giants)
•

•

•

of an H-R diagram

Very large giants are called supergiants
Only a few percent of all stars

White dwarfs
•
•

•
•
•

Fainter than main-sequence stars
Small (approximate the size of Earth)
Lower-central area on the H-R diagram
Not all are white in color
Perhaps 10% of all stars

Idealized HertzsprungRussell diagram

Figure 24.5

Quiz Break

24.2 Variable stars
 Stars

that fluctuate in brightness
 Types of variable stars
•

Pulsating variables
•
•

•

Fluctuate regularly in brightness
Expand and contract in size

Eruptive variables
•
•
•

Explosive event
Sudden brightening
Called a nova

24.2 Interstellar matter
 Between

the stars is "the vacuum of

space"
 Nebula
•
•

Cloud of dust and gases
Two major types of nebulae
•

Bright nebula
• Glows if it close to a very hot star
• Two types of bright nebulae
• Emission nebula
• Reflection nebula

The Orion Nebula is a wellknown emission nebula

Figure 24.8

A faint blue reflection nebula in
the Pleiades star cluster

Figure 24.9

24.2 Interstellar matter (continued)
 Nebula
•

Two major types of nebulae
•

Dark nebula
• Not close to any bright star
• Appear dark
• Contains the material that forms stars and
planets

24.2 Stellar evolution
 Stars

exist because of gravity
 Two opposing forces in a star are
•
•

Gravity – contracts
Thermal nuclear energy – expands

 Stages
•

Birth
•

•
•
•
•

In dark, cool, interstellar clouds
Gravity contracts the cloud
Temperature rises
Radiates long-wavelength (red) light
Becomes a protostar

24.2 Stellar evolution (continued)
 Stages
•

Protostar
•
•
•

•
•
•
•

Gravitational contraction of gaseous cloud
continues
Core reaches 10 million K
Hydrogen nuclei fuse
• Become helium nuclei
• Process is called hydrogen burning
Energy is released
Outward pressure increases
Outward pressure balanced by gravity pulling in
Star becomes a stable main-sequence star

24.2 Stellar evolution (continued)
 Stages
•

Main-sequence stage
•

Stars age at different rates
• Massive stars use fuel faster and exist for
only a few million years
• Small stars use fuel slowly and exist for
perhaps hundreds of billions of years

•

90% of a star's life is in the main-sequence

24.2 Stellar evolution (continued)
 Stages
•

Red giant stage
•
•

•
•
•

Hydrogen burning migrates outward
Star's outer envelope expands
• Surface cools
• Surface becomes red
Core is collapsing as helium is converted to
carbon
Eventually all nuclear fuel is used
Gravity squeezes the star

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Low-mass star
• 0.5 solar mass
• Red giant collapses
• Becomes a white dwarf

24.2 Evolutionary stages of
low mass stars

Figure 24.12 A

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Medium-mass star
• Between 0.5 and 3 solar masses
• Red giant collapses
• Planetary nebula forms
• Becomes a white dwarf

24.2 Evolutionary stages of
medium mass stars

Figure 24.12 B

H-R diagram showing
stellar evolution

Figure 24.11

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Massive star
• Over 3 solar masses
• Short life span
• Terminates in a brilliant explosion called
a supernova
• Interior condenses
• May produce a hot, dense object that is
either a neutron star or a black hole

24.2 Evolutionary stages of
massive stars

Figure 24.12 C

24.2 Stellar remnants
 White
•
•

Small (some no larger than Earth)
Dense
•
•
•

•
•

dwarf

Can be more massive than the Sun
Spoonful weighs several tons
Atoms take up less space
• Electrons displaced inward
• Called degenerate matter

Hot surface
Cools to become a black dwarf

24.2 Stellar remnants (continued)
 Neutron
•

Forms from a more massive star
•
•

•
•

star

Star has more gravity
Squeezes itself smaller

Remnant of a supernova
Gravitational force collapses atoms
•
•

Electrons combine with protons to produce
neutrons
Small size

24.2 Stellar remnants (continued)
 Neutron
•

Pea size sample
•
•

•
•

star

Weighs 100 million tons
Same density as an atomic nucleus

Strong magnetic field
First one discovered in early 1970s
•
•

Pulsar (pulsating radio source)
Found in the Crab nebula (remnant of an A.D.
1054 supernova)

Crab Nebula in the
constellation Taurus

Figure 24.14

24.2 Stellar remnants (continued)
 Black
•
•

•

More dense than a neutron star
Intense surface gravity lets no light escape
As matter is pulled into it
•
•

•

hole

Becomes very hot
Emits x-rays

Likely candidate is Cygnus X-1, a strong xray source

Quiz Break

24.3 Galaxies
 Milky
•

Way galaxy

Structure
•
•

•
•

Determined by using radio telescopes
Large spiral galaxy
• About 100,000 light-years wide
• Thickness at the galactic nucleus is about
10,000 light-years
Three spiral arms of stars
Sun is 30,000 light-years from the center

Face-on view of the
Milk Way Galaxy

Figure 24.18 A

Edge-on view of the
Milk Way Galaxy

Figure 24.18 B

24.3 Galaxies (continued)
 Milky
•

Rotation
•
•
•

•

Way galaxy

Around the galactic nucleus
Outermost stars move the slowest
Sun rotates around the galactic nucleus once
about every 200 million years

Halo surrounds the galactic disk
•
•
•

Spherical
Very tenuous gas
Numerous globular clusters

24.3 Galaxies (continued)
 Other
•
•

galaxies

Existence was first proposed in mid-1700s
by Immanuel Kant
Four basic types of galaxies
•

Spiral galaxy
• Arms extending from nucleus
• About 30% of all galaxies
• Large diameter of 20,000 to 125,000 light
years
• Contains both young and old stars
• e.g., Milky Way

Great Galaxy, a spiral galaxy, in
the constellation Andromeda

Figure 24.20

24.3 Galaxies (continued)
 Other
•

galaxies

Four basic types of galaxies
•

•

Barred spiral galaxy
• Stars arranged in the shape of a bar
• Generally quite large
• About 10% of all galaxies
Elliptical galaxy
• Ellipsoidal shape
• About 60% of all galaxies
• Most are smaller than spiral galaxies;
however, they are also the largest known
galaxies

A barred spiral galaxy

Figure 24.22

24.3 Galaxies (continued)
 Other
•

galaxies

Four basic types of galaxies
•

Irregular galaxy
• Lacks symmetry
• About 10% of all galaxies
• Contains mostly young stars
• e.g., Magellanic Clouds

24.3 Galaxies (continued)
 Galactic
•
•
•

Group of galaxies
Some contain thousands of galaxies
Local Group
•
•

•

cluster

Our own group of galaxies
Contains at least 28 galaxies

Supercluster
•
•

Huge swarm of galaxies
May be the largest entity in the universe

Quiz Break

24.4 Red shifts
 Doppler
•

effect

Change in the wavelength of light emitted
by an object due to its motion
•

•

Movement away stretches the wavelength
• Longer wavelength
• Light appears redder
Movement toward “squeezes” the wavelength
• Shorter wavelength
• Light shifted toward the blue

24.4 Red shifts (continued)
 Doppler
•

effect

Amount of the Doppler shift indicates the
rate of movement
•
•

Large Doppler shift indicates a high velocity
Small Doppler shift indicates a lower velocity

 Expanding
•

universe

Most galaxies exhibit a red Doppler shift
•

Moving away

Raisin bread analogy of an
expanding universe

Figure 24.24

24.4 Red shifts (continued)
 Expanding
•

universe

Most galaxies exhibit a red Doppler shift
•

•
•
•

Far galaxies
• Exhibit the greatest shift
• Greater velocity
Discovered in 1929 by Edwin Hubble
Hubble's Law – the recessional speed of
galaxies is proportional to their distance
Accounts for red shifts

24.4 Big Bang theory
 Accounts

for galaxies moving away

from us
 Universe was once confined to a "ball"
that was
•
•

•

Supermassive
Dense
Hot

24.4 Big Bang theory (continued)
 Big

Bang marks the inception of the
universe
•
•

Occurred about 15 billion years ago
All matter and space was created

 Matter

is moving outward
 Fate of the universe
•

Two possibilities
•
•

Universe will last forever
Outward expansion sill stop and gravitational;
contraction will follow

24.4 Big Bang theory (continued)
 Fate
•

of the universe

Final fate depends on the average density
of the universe
•
•

If the density is more than the critical density,
then the universe would contract
Current estimates point to less then the critical
density and predict an ever-expanding, or
open, universe

Chapter 24Test Guidance
You will be responsible on the test for answering 3 of the following 6
questions.
1.

2.

3.
4.
5.
6.

What causes the difference between a star’s apparent
magnitude and it absolute magnitude.
List and explain the three factors that control the apparent
brightness of a star as seen from Earth.
Describe how binary stars are used to determine stellar mass.
List and describe the four basic types of galaxies.
What is Hubble’s Law, please explain in detail.
Briefly describe the Big Bang Theory (not the TV show).

End of Chapter 24


Slide 27

Lecture Outlines
PowerPoint

Chapter 24
Earth Science 11e
Tarbuck/Lutgens
Modified for educational
purposes only
By S. Koziol 12-8-2010

© 2006 Pearson Prentice Hall

Earth Science, 11e
Beyond Our
Solar System
Chapter 24

24.1 Properties of stars
 Distance
•
•

Measuring a star's distance can be very
difficult
Stellar parallax
•
•
•

•
•

Used for measuring distance to a star
Apparent shift in a star's position due to the
orbital motion of Earth
Measured as an angle
Near stars have the largest parallax
Largest parallax is less than one second of arc

24. 1 Properties of stars
(continued)

 Distance
•
•

Distances to the stars are very large
Units of measurement
•
•

•

Kilometers or astronomical units are too
cumbersome to use
Light-year is used most often
• Distance that light travels in 1 year
• One light-year is 9.5 trillion km (5.8 trillion
miles)

Other methods for measuring distance are
also used

24. 1 Properties of stars
(continued)

 Stellar
•

Controlled by three factors
•

•
•

•

brightness

Size
Temperature
Distance

Magnitude
•

Measure of a star's brightness

24.1 Properties of stars
(continued)

 Stellar
•

brightness

Magnitude
•

Two types of measurement
• Apparent magnitude
• Brightness when a star is viewed from
Earth
• Decreases with distance
• Numbers are used to designate
magnitudes - dim stars have large
numbers and negative numbers are also
used

24.1 Properties of stars
(continued)

 Stellar
•

brightness

Magnitude
•

Two types of measurement
• Absolute magnitude
• "True" or intrinsic brightness of a star
• Brightness at a standard distance of
32.6 light-years
• Most stars' absolute magnitudes are
between -5 and +15

24.1 Properties of stars
(continued)

 Color
•

Hot star
•

•
•

•

and temperature

Temperature above 30,000 K
Emits short-wavelength light
Appears blue

Cool star
•
•
•

Temperature less than 3000 K
Emits longer-wavelength light
Appears red

24.1 Properties of stars
(continued)

 Color
•

and temperature

Between 5000 and 6000 K
•
•

Stars appear yellow
e.g., Sun

 Binary
•

stars and stellar mass

Binary stars
•

Two stars orbiting one another
• Stars are held together by mutual
gravitation
• Both orbit around a common center of mass

24.1 Properties of stars (continued)
 Binary
•

Binary stars
•

•
•

•

stars and stellar mass

Visual binaries are resolved telescopically
More than 50% of the stars in the universe are
binary stars
Used to determine stellar mass

Stellar mass
•

Determined using binary stars – the center of
mass is closest to the most massive star

Binary stars
orbit each
other around
their common
center of
mass
Figure 24.4

24.1 Properties of stars (continued)
 Binary
•

stars and stellar mass

Stellar mass
•

Mass of most stars is between one-tenth and
fifty times the mass of the Sun

24.1 Hertzsprung-Russell
diagram
 Shows
•
•

the relation between stellar

Brightness (absolute magnitude) and
Temperature

 Diagram

is made by plotting (graphing)
each star's
•
•

Luminosity (brightness) and
Temperature

24.1 Hertzsprung-Russell
diagram (continued)
 Parts
•

Main-sequence stars
•

•
•

•

of an H-R diagram

90% of all stars
Band through the center of the H-R diagram
Sun is in the main-sequence

Giants (or red giants)
•
•
•

Very luminous
Large
Upper-right on the H-R diagram

24.1 Hertzsprung-Russell
diagram (continued)
 Parts
•

Giants (or red giants)
•

•

•

of an H-R diagram

Very large giants are called supergiants
Only a few percent of all stars

White dwarfs
•
•

•
•
•

Fainter than main-sequence stars
Small (approximate the size of Earth)
Lower-central area on the H-R diagram
Not all are white in color
Perhaps 10% of all stars

Idealized HertzsprungRussell diagram

Figure 24.5

Quiz Break

24.2 Variable stars
 Stars

that fluctuate in brightness
 Types of variable stars
•

Pulsating variables
•
•

•

Fluctuate regularly in brightness
Expand and contract in size

Eruptive variables
•
•
•

Explosive event
Sudden brightening
Called a nova

24.2 Interstellar matter
 Between

the stars is "the vacuum of

space"
 Nebula
•
•

Cloud of dust and gases
Two major types of nebulae
•

Bright nebula
• Glows if it close to a very hot star
• Two types of bright nebulae
• Emission nebula
• Reflection nebula

The Orion Nebula is a wellknown emission nebula

Figure 24.8

A faint blue reflection nebula in
the Pleiades star cluster

Figure 24.9

24.2 Interstellar matter (continued)
 Nebula
•

Two major types of nebulae
•

Dark nebula
• Not close to any bright star
• Appear dark
• Contains the material that forms stars and
planets

24.2 Stellar evolution
 Stars

exist because of gravity
 Two opposing forces in a star are
•
•

Gravity – contracts
Thermal nuclear energy – expands

 Stages
•

Birth
•

•
•
•
•

In dark, cool, interstellar clouds
Gravity contracts the cloud
Temperature rises
Radiates long-wavelength (red) light
Becomes a protostar

24.2 Stellar evolution (continued)
 Stages
•

Protostar
•
•
•

•
•
•
•

Gravitational contraction of gaseous cloud
continues
Core reaches 10 million K
Hydrogen nuclei fuse
• Become helium nuclei
• Process is called hydrogen burning
Energy is released
Outward pressure increases
Outward pressure balanced by gravity pulling in
Star becomes a stable main-sequence star

24.2 Stellar evolution (continued)
 Stages
•

Main-sequence stage
•

Stars age at different rates
• Massive stars use fuel faster and exist for
only a few million years
• Small stars use fuel slowly and exist for
perhaps hundreds of billions of years

•

90% of a star's life is in the main-sequence

24.2 Stellar evolution (continued)
 Stages
•

Red giant stage
•
•

•
•
•

Hydrogen burning migrates outward
Star's outer envelope expands
• Surface cools
• Surface becomes red
Core is collapsing as helium is converted to
carbon
Eventually all nuclear fuel is used
Gravity squeezes the star

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Low-mass star
• 0.5 solar mass
• Red giant collapses
• Becomes a white dwarf

24.2 Evolutionary stages of
low mass stars

Figure 24.12 A

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Medium-mass star
• Between 0.5 and 3 solar masses
• Red giant collapses
• Planetary nebula forms
• Becomes a white dwarf

24.2 Evolutionary stages of
medium mass stars

Figure 24.12 B

H-R diagram showing
stellar evolution

Figure 24.11

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Massive star
• Over 3 solar masses
• Short life span
• Terminates in a brilliant explosion called
a supernova
• Interior condenses
• May produce a hot, dense object that is
either a neutron star or a black hole

24.2 Evolutionary stages of
massive stars

Figure 24.12 C

24.2 Stellar remnants
 White
•
•

Small (some no larger than Earth)
Dense
•
•
•

•
•

dwarf

Can be more massive than the Sun
Spoonful weighs several tons
Atoms take up less space
• Electrons displaced inward
• Called degenerate matter

Hot surface
Cools to become a black dwarf

24.2 Stellar remnants (continued)
 Neutron
•

Forms from a more massive star
•
•

•
•

star

Star has more gravity
Squeezes itself smaller

Remnant of a supernova
Gravitational force collapses atoms
•
•

Electrons combine with protons to produce
neutrons
Small size

24.2 Stellar remnants (continued)
 Neutron
•

Pea size sample
•
•

•
•

star

Weighs 100 million tons
Same density as an atomic nucleus

Strong magnetic field
First one discovered in early 1970s
•
•

Pulsar (pulsating radio source)
Found in the Crab nebula (remnant of an A.D.
1054 supernova)

Crab Nebula in the
constellation Taurus

Figure 24.14

24.2 Stellar remnants (continued)
 Black
•
•

•

More dense than a neutron star
Intense surface gravity lets no light escape
As matter is pulled into it
•
•

•

hole

Becomes very hot
Emits x-rays

Likely candidate is Cygnus X-1, a strong xray source

Quiz Break

24.3 Galaxies
 Milky
•

Way galaxy

Structure
•
•

•
•

Determined by using radio telescopes
Large spiral galaxy
• About 100,000 light-years wide
• Thickness at the galactic nucleus is about
10,000 light-years
Three spiral arms of stars
Sun is 30,000 light-years from the center

Face-on view of the
Milk Way Galaxy

Figure 24.18 A

Edge-on view of the
Milk Way Galaxy

Figure 24.18 B

24.3 Galaxies (continued)
 Milky
•

Rotation
•
•
•

•

Way galaxy

Around the galactic nucleus
Outermost stars move the slowest
Sun rotates around the galactic nucleus once
about every 200 million years

Halo surrounds the galactic disk
•
•
•

Spherical
Very tenuous gas
Numerous globular clusters

24.3 Galaxies (continued)
 Other
•
•

galaxies

Existence was first proposed in mid-1700s
by Immanuel Kant
Four basic types of galaxies
•

Spiral galaxy
• Arms extending from nucleus
• About 30% of all galaxies
• Large diameter of 20,000 to 125,000 light
years
• Contains both young and old stars
• e.g., Milky Way

Great Galaxy, a spiral galaxy, in
the constellation Andromeda

Figure 24.20

24.3 Galaxies (continued)
 Other
•

galaxies

Four basic types of galaxies
•

•

Barred spiral galaxy
• Stars arranged in the shape of a bar
• Generally quite large
• About 10% of all galaxies
Elliptical galaxy
• Ellipsoidal shape
• About 60% of all galaxies
• Most are smaller than spiral galaxies;
however, they are also the largest known
galaxies

A barred spiral galaxy

Figure 24.22

24.3 Galaxies (continued)
 Other
•

galaxies

Four basic types of galaxies
•

Irregular galaxy
• Lacks symmetry
• About 10% of all galaxies
• Contains mostly young stars
• e.g., Magellanic Clouds

24.3 Galaxies (continued)
 Galactic
•
•
•

Group of galaxies
Some contain thousands of galaxies
Local Group
•
•

•

cluster

Our own group of galaxies
Contains at least 28 galaxies

Supercluster
•
•

Huge swarm of galaxies
May be the largest entity in the universe

Quiz Break

24.4 Red shifts
 Doppler
•

effect

Change in the wavelength of light emitted
by an object due to its motion
•

•

Movement away stretches the wavelength
• Longer wavelength
• Light appears redder
Movement toward “squeezes” the wavelength
• Shorter wavelength
• Light shifted toward the blue

24.4 Red shifts (continued)
 Doppler
•

effect

Amount of the Doppler shift indicates the
rate of movement
•
•

Large Doppler shift indicates a high velocity
Small Doppler shift indicates a lower velocity

 Expanding
•

universe

Most galaxies exhibit a red Doppler shift
•

Moving away

Raisin bread analogy of an
expanding universe

Figure 24.24

24.4 Red shifts (continued)
 Expanding
•

universe

Most galaxies exhibit a red Doppler shift
•

•
•
•

Far galaxies
• Exhibit the greatest shift
• Greater velocity
Discovered in 1929 by Edwin Hubble
Hubble's Law – the recessional speed of
galaxies is proportional to their distance
Accounts for red shifts

24.4 Big Bang theory
 Accounts

for galaxies moving away

from us
 Universe was once confined to a "ball"
that was
•
•

•

Supermassive
Dense
Hot

24.4 Big Bang theory (continued)
 Big

Bang marks the inception of the
universe
•
•

Occurred about 15 billion years ago
All matter and space was created

 Matter

is moving outward
 Fate of the universe
•

Two possibilities
•
•

Universe will last forever
Outward expansion sill stop and gravitational;
contraction will follow

24.4 Big Bang theory (continued)
 Fate
•

of the universe

Final fate depends on the average density
of the universe
•
•

If the density is more than the critical density,
then the universe would contract
Current estimates point to less then the critical
density and predict an ever-expanding, or
open, universe

Chapter 24Test Guidance
You will be responsible on the test for answering 3 of the following 6
questions.
1.

2.

3.
4.
5.
6.

What causes the difference between a star’s apparent
magnitude and it absolute magnitude.
List and explain the three factors that control the apparent
brightness of a star as seen from Earth.
Describe how binary stars are used to determine stellar mass.
List and describe the four basic types of galaxies.
What is Hubble’s Law, please explain in detail.
Briefly describe the Big Bang Theory (not the TV show).

End of Chapter 24


Slide 28

Lecture Outlines
PowerPoint

Chapter 24
Earth Science 11e
Tarbuck/Lutgens
Modified for educational
purposes only
By S. Koziol 12-8-2010

© 2006 Pearson Prentice Hall

Earth Science, 11e
Beyond Our
Solar System
Chapter 24

24.1 Properties of stars
 Distance
•
•

Measuring a star's distance can be very
difficult
Stellar parallax
•
•
•

•
•

Used for measuring distance to a star
Apparent shift in a star's position due to the
orbital motion of Earth
Measured as an angle
Near stars have the largest parallax
Largest parallax is less than one second of arc

24. 1 Properties of stars
(continued)

 Distance
•
•

Distances to the stars are very large
Units of measurement
•
•

•

Kilometers or astronomical units are too
cumbersome to use
Light-year is used most often
• Distance that light travels in 1 year
• One light-year is 9.5 trillion km (5.8 trillion
miles)

Other methods for measuring distance are
also used

24. 1 Properties of stars
(continued)

 Stellar
•

Controlled by three factors
•

•
•

•

brightness

Size
Temperature
Distance

Magnitude
•

Measure of a star's brightness

24.1 Properties of stars
(continued)

 Stellar
•

brightness

Magnitude
•

Two types of measurement
• Apparent magnitude
• Brightness when a star is viewed from
Earth
• Decreases with distance
• Numbers are used to designate
magnitudes - dim stars have large
numbers and negative numbers are also
used

24.1 Properties of stars
(continued)

 Stellar
•

brightness

Magnitude
•

Two types of measurement
• Absolute magnitude
• "True" or intrinsic brightness of a star
• Brightness at a standard distance of
32.6 light-years
• Most stars' absolute magnitudes are
between -5 and +15

24.1 Properties of stars
(continued)

 Color
•

Hot star
•

•
•

•

and temperature

Temperature above 30,000 K
Emits short-wavelength light
Appears blue

Cool star
•
•
•

Temperature less than 3000 K
Emits longer-wavelength light
Appears red

24.1 Properties of stars
(continued)

 Color
•

and temperature

Between 5000 and 6000 K
•
•

Stars appear yellow
e.g., Sun

 Binary
•

stars and stellar mass

Binary stars
•

Two stars orbiting one another
• Stars are held together by mutual
gravitation
• Both orbit around a common center of mass

24.1 Properties of stars (continued)
 Binary
•

Binary stars
•

•
•

•

stars and stellar mass

Visual binaries are resolved telescopically
More than 50% of the stars in the universe are
binary stars
Used to determine stellar mass

Stellar mass
•

Determined using binary stars – the center of
mass is closest to the most massive star

Binary stars
orbit each
other around
their common
center of
mass
Figure 24.4

24.1 Properties of stars (continued)
 Binary
•

stars and stellar mass

Stellar mass
•

Mass of most stars is between one-tenth and
fifty times the mass of the Sun

24.1 Hertzsprung-Russell
diagram
 Shows
•
•

the relation between stellar

Brightness (absolute magnitude) and
Temperature

 Diagram

is made by plotting (graphing)
each star's
•
•

Luminosity (brightness) and
Temperature

24.1 Hertzsprung-Russell
diagram (continued)
 Parts
•

Main-sequence stars
•

•
•

•

of an H-R diagram

90% of all stars
Band through the center of the H-R diagram
Sun is in the main-sequence

Giants (or red giants)
•
•
•

Very luminous
Large
Upper-right on the H-R diagram

24.1 Hertzsprung-Russell
diagram (continued)
 Parts
•

Giants (or red giants)
•

•

•

of an H-R diagram

Very large giants are called supergiants
Only a few percent of all stars

White dwarfs
•
•

•
•
•

Fainter than main-sequence stars
Small (approximate the size of Earth)
Lower-central area on the H-R diagram
Not all are white in color
Perhaps 10% of all stars

Idealized HertzsprungRussell diagram

Figure 24.5

Quiz Break

24.2 Variable stars
 Stars

that fluctuate in brightness
 Types of variable stars
•

Pulsating variables
•
•

•

Fluctuate regularly in brightness
Expand and contract in size

Eruptive variables
•
•
•

Explosive event
Sudden brightening
Called a nova

24.2 Interstellar matter
 Between

the stars is "the vacuum of

space"
 Nebula
•
•

Cloud of dust and gases
Two major types of nebulae
•

Bright nebula
• Glows if it close to a very hot star
• Two types of bright nebulae
• Emission nebula
• Reflection nebula

The Orion Nebula is a wellknown emission nebula

Figure 24.8

A faint blue reflection nebula in
the Pleiades star cluster

Figure 24.9

24.2 Interstellar matter (continued)
 Nebula
•

Two major types of nebulae
•

Dark nebula
• Not close to any bright star
• Appear dark
• Contains the material that forms stars and
planets

24.2 Stellar evolution
 Stars

exist because of gravity
 Two opposing forces in a star are
•
•

Gravity – contracts
Thermal nuclear energy – expands

 Stages
•

Birth
•

•
•
•
•

In dark, cool, interstellar clouds
Gravity contracts the cloud
Temperature rises
Radiates long-wavelength (red) light
Becomes a protostar

24.2 Stellar evolution (continued)
 Stages
•

Protostar
•
•
•

•
•
•
•

Gravitational contraction of gaseous cloud
continues
Core reaches 10 million K
Hydrogen nuclei fuse
• Become helium nuclei
• Process is called hydrogen burning
Energy is released
Outward pressure increases
Outward pressure balanced by gravity pulling in
Star becomes a stable main-sequence star

24.2 Stellar evolution (continued)
 Stages
•

Main-sequence stage
•

Stars age at different rates
• Massive stars use fuel faster and exist for
only a few million years
• Small stars use fuel slowly and exist for
perhaps hundreds of billions of years

•

90% of a star's life is in the main-sequence

24.2 Stellar evolution (continued)
 Stages
•

Red giant stage
•
•

•
•
•

Hydrogen burning migrates outward
Star's outer envelope expands
• Surface cools
• Surface becomes red
Core is collapsing as helium is converted to
carbon
Eventually all nuclear fuel is used
Gravity squeezes the star

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Low-mass star
• 0.5 solar mass
• Red giant collapses
• Becomes a white dwarf

24.2 Evolutionary stages of
low mass stars

Figure 24.12 A

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Medium-mass star
• Between 0.5 and 3 solar masses
• Red giant collapses
• Planetary nebula forms
• Becomes a white dwarf

24.2 Evolutionary stages of
medium mass stars

Figure 24.12 B

H-R diagram showing
stellar evolution

Figure 24.11

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Massive star
• Over 3 solar masses
• Short life span
• Terminates in a brilliant explosion called
a supernova
• Interior condenses
• May produce a hot, dense object that is
either a neutron star or a black hole

24.2 Evolutionary stages of
massive stars

Figure 24.12 C

24.2 Stellar remnants
 White
•
•

Small (some no larger than Earth)
Dense
•
•
•

•
•

dwarf

Can be more massive than the Sun
Spoonful weighs several tons
Atoms take up less space
• Electrons displaced inward
• Called degenerate matter

Hot surface
Cools to become a black dwarf

24.2 Stellar remnants (continued)
 Neutron
•

Forms from a more massive star
•
•

•
•

star

Star has more gravity
Squeezes itself smaller

Remnant of a supernova
Gravitational force collapses atoms
•
•

Electrons combine with protons to produce
neutrons
Small size

24.2 Stellar remnants (continued)
 Neutron
•

Pea size sample
•
•

•
•

star

Weighs 100 million tons
Same density as an atomic nucleus

Strong magnetic field
First one discovered in early 1970s
•
•

Pulsar (pulsating radio source)
Found in the Crab nebula (remnant of an A.D.
1054 supernova)

Crab Nebula in the
constellation Taurus

Figure 24.14

24.2 Stellar remnants (continued)
 Black
•
•

•

More dense than a neutron star
Intense surface gravity lets no light escape
As matter is pulled into it
•
•

•

hole

Becomes very hot
Emits x-rays

Likely candidate is Cygnus X-1, a strong xray source

Quiz Break

24.3 Galaxies
 Milky
•

Way galaxy

Structure
•
•

•
•

Determined by using radio telescopes
Large spiral galaxy
• About 100,000 light-years wide
• Thickness at the galactic nucleus is about
10,000 light-years
Three spiral arms of stars
Sun is 30,000 light-years from the center

Face-on view of the
Milk Way Galaxy

Figure 24.18 A

Edge-on view of the
Milk Way Galaxy

Figure 24.18 B

24.3 Galaxies (continued)
 Milky
•

Rotation
•
•
•

•

Way galaxy

Around the galactic nucleus
Outermost stars move the slowest
Sun rotates around the galactic nucleus once
about every 200 million years

Halo surrounds the galactic disk
•
•
•

Spherical
Very tenuous gas
Numerous globular clusters

24.3 Galaxies (continued)
 Other
•
•

galaxies

Existence was first proposed in mid-1700s
by Immanuel Kant
Four basic types of galaxies
•

Spiral galaxy
• Arms extending from nucleus
• About 30% of all galaxies
• Large diameter of 20,000 to 125,000 light
years
• Contains both young and old stars
• e.g., Milky Way

Great Galaxy, a spiral galaxy, in
the constellation Andromeda

Figure 24.20

24.3 Galaxies (continued)
 Other
•

galaxies

Four basic types of galaxies
•

•

Barred spiral galaxy
• Stars arranged in the shape of a bar
• Generally quite large
• About 10% of all galaxies
Elliptical galaxy
• Ellipsoidal shape
• About 60% of all galaxies
• Most are smaller than spiral galaxies;
however, they are also the largest known
galaxies

A barred spiral galaxy

Figure 24.22

24.3 Galaxies (continued)
 Other
•

galaxies

Four basic types of galaxies
•

Irregular galaxy
• Lacks symmetry
• About 10% of all galaxies
• Contains mostly young stars
• e.g., Magellanic Clouds

24.3 Galaxies (continued)
 Galactic
•
•
•

Group of galaxies
Some contain thousands of galaxies
Local Group
•
•

•

cluster

Our own group of galaxies
Contains at least 28 galaxies

Supercluster
•
•

Huge swarm of galaxies
May be the largest entity in the universe

Quiz Break

24.4 Red shifts
 Doppler
•

effect

Change in the wavelength of light emitted
by an object due to its motion
•

•

Movement away stretches the wavelength
• Longer wavelength
• Light appears redder
Movement toward “squeezes” the wavelength
• Shorter wavelength
• Light shifted toward the blue

24.4 Red shifts (continued)
 Doppler
•

effect

Amount of the Doppler shift indicates the
rate of movement
•
•

Large Doppler shift indicates a high velocity
Small Doppler shift indicates a lower velocity

 Expanding
•

universe

Most galaxies exhibit a red Doppler shift
•

Moving away

Raisin bread analogy of an
expanding universe

Figure 24.24

24.4 Red shifts (continued)
 Expanding
•

universe

Most galaxies exhibit a red Doppler shift
•

•
•
•

Far galaxies
• Exhibit the greatest shift
• Greater velocity
Discovered in 1929 by Edwin Hubble
Hubble's Law – the recessional speed of
galaxies is proportional to their distance
Accounts for red shifts

24.4 Big Bang theory
 Accounts

for galaxies moving away

from us
 Universe was once confined to a "ball"
that was
•
•

•

Supermassive
Dense
Hot

24.4 Big Bang theory (continued)
 Big

Bang marks the inception of the
universe
•
•

Occurred about 15 billion years ago
All matter and space was created

 Matter

is moving outward
 Fate of the universe
•

Two possibilities
•
•

Universe will last forever
Outward expansion sill stop and gravitational;
contraction will follow

24.4 Big Bang theory (continued)
 Fate
•

of the universe

Final fate depends on the average density
of the universe
•
•

If the density is more than the critical density,
then the universe would contract
Current estimates point to less then the critical
density and predict an ever-expanding, or
open, universe

Chapter 24Test Guidance
You will be responsible on the test for answering 3 of the following 6
questions.
1.

2.

3.
4.
5.
6.

What causes the difference between a star’s apparent
magnitude and it absolute magnitude.
List and explain the three factors that control the apparent
brightness of a star as seen from Earth.
Describe how binary stars are used to determine stellar mass.
List and describe the four basic types of galaxies.
What is Hubble’s Law, please explain in detail.
Briefly describe the Big Bang Theory (not the TV show).

End of Chapter 24


Slide 29

Lecture Outlines
PowerPoint

Chapter 24
Earth Science 11e
Tarbuck/Lutgens
Modified for educational
purposes only
By S. Koziol 12-8-2010

© 2006 Pearson Prentice Hall

Earth Science, 11e
Beyond Our
Solar System
Chapter 24

24.1 Properties of stars
 Distance
•
•

Measuring a star's distance can be very
difficult
Stellar parallax
•
•
•

•
•

Used for measuring distance to a star
Apparent shift in a star's position due to the
orbital motion of Earth
Measured as an angle
Near stars have the largest parallax
Largest parallax is less than one second of arc

24. 1 Properties of stars
(continued)

 Distance
•
•

Distances to the stars are very large
Units of measurement
•
•

•

Kilometers or astronomical units are too
cumbersome to use
Light-year is used most often
• Distance that light travels in 1 year
• One light-year is 9.5 trillion km (5.8 trillion
miles)

Other methods for measuring distance are
also used

24. 1 Properties of stars
(continued)

 Stellar
•

Controlled by three factors
•

•
•

•

brightness

Size
Temperature
Distance

Magnitude
•

Measure of a star's brightness

24.1 Properties of stars
(continued)

 Stellar
•

brightness

Magnitude
•

Two types of measurement
• Apparent magnitude
• Brightness when a star is viewed from
Earth
• Decreases with distance
• Numbers are used to designate
magnitudes - dim stars have large
numbers and negative numbers are also
used

24.1 Properties of stars
(continued)

 Stellar
•

brightness

Magnitude
•

Two types of measurement
• Absolute magnitude
• "True" or intrinsic brightness of a star
• Brightness at a standard distance of
32.6 light-years
• Most stars' absolute magnitudes are
between -5 and +15

24.1 Properties of stars
(continued)

 Color
•

Hot star
•

•
•

•

and temperature

Temperature above 30,000 K
Emits short-wavelength light
Appears blue

Cool star
•
•
•

Temperature less than 3000 K
Emits longer-wavelength light
Appears red

24.1 Properties of stars
(continued)

 Color
•

and temperature

Between 5000 and 6000 K
•
•

Stars appear yellow
e.g., Sun

 Binary
•

stars and stellar mass

Binary stars
•

Two stars orbiting one another
• Stars are held together by mutual
gravitation
• Both orbit around a common center of mass

24.1 Properties of stars (continued)
 Binary
•

Binary stars
•

•
•

•

stars and stellar mass

Visual binaries are resolved telescopically
More than 50% of the stars in the universe are
binary stars
Used to determine stellar mass

Stellar mass
•

Determined using binary stars – the center of
mass is closest to the most massive star

Binary stars
orbit each
other around
their common
center of
mass
Figure 24.4

24.1 Properties of stars (continued)
 Binary
•

stars and stellar mass

Stellar mass
•

Mass of most stars is between one-tenth and
fifty times the mass of the Sun

24.1 Hertzsprung-Russell
diagram
 Shows
•
•

the relation between stellar

Brightness (absolute magnitude) and
Temperature

 Diagram

is made by plotting (graphing)
each star's
•
•

Luminosity (brightness) and
Temperature

24.1 Hertzsprung-Russell
diagram (continued)
 Parts
•

Main-sequence stars
•

•
•

•

of an H-R diagram

90% of all stars
Band through the center of the H-R diagram
Sun is in the main-sequence

Giants (or red giants)
•
•
•

Very luminous
Large
Upper-right on the H-R diagram

24.1 Hertzsprung-Russell
diagram (continued)
 Parts
•

Giants (or red giants)
•

•

•

of an H-R diagram

Very large giants are called supergiants
Only a few percent of all stars

White dwarfs
•
•

•
•
•

Fainter than main-sequence stars
Small (approximate the size of Earth)
Lower-central area on the H-R diagram
Not all are white in color
Perhaps 10% of all stars

Idealized HertzsprungRussell diagram

Figure 24.5

Quiz Break

24.2 Variable stars
 Stars

that fluctuate in brightness
 Types of variable stars
•

Pulsating variables
•
•

•

Fluctuate regularly in brightness
Expand and contract in size

Eruptive variables
•
•
•

Explosive event
Sudden brightening
Called a nova

24.2 Interstellar matter
 Between

the stars is "the vacuum of

space"
 Nebula
•
•

Cloud of dust and gases
Two major types of nebulae
•

Bright nebula
• Glows if it close to a very hot star
• Two types of bright nebulae
• Emission nebula
• Reflection nebula

The Orion Nebula is a wellknown emission nebula

Figure 24.8

A faint blue reflection nebula in
the Pleiades star cluster

Figure 24.9

24.2 Interstellar matter (continued)
 Nebula
•

Two major types of nebulae
•

Dark nebula
• Not close to any bright star
• Appear dark
• Contains the material that forms stars and
planets

24.2 Stellar evolution
 Stars

exist because of gravity
 Two opposing forces in a star are
•
•

Gravity – contracts
Thermal nuclear energy – expands

 Stages
•

Birth
•

•
•
•
•

In dark, cool, interstellar clouds
Gravity contracts the cloud
Temperature rises
Radiates long-wavelength (red) light
Becomes a protostar

24.2 Stellar evolution (continued)
 Stages
•

Protostar
•
•
•

•
•
•
•

Gravitational contraction of gaseous cloud
continues
Core reaches 10 million K
Hydrogen nuclei fuse
• Become helium nuclei
• Process is called hydrogen burning
Energy is released
Outward pressure increases
Outward pressure balanced by gravity pulling in
Star becomes a stable main-sequence star

24.2 Stellar evolution (continued)
 Stages
•

Main-sequence stage
•

Stars age at different rates
• Massive stars use fuel faster and exist for
only a few million years
• Small stars use fuel slowly and exist for
perhaps hundreds of billions of years

•

90% of a star's life is in the main-sequence

24.2 Stellar evolution (continued)
 Stages
•

Red giant stage
•
•

•
•
•

Hydrogen burning migrates outward
Star's outer envelope expands
• Surface cools
• Surface becomes red
Core is collapsing as helium is converted to
carbon
Eventually all nuclear fuel is used
Gravity squeezes the star

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Low-mass star
• 0.5 solar mass
• Red giant collapses
• Becomes a white dwarf

24.2 Evolutionary stages of
low mass stars

Figure 24.12 A

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Medium-mass star
• Between 0.5 and 3 solar masses
• Red giant collapses
• Planetary nebula forms
• Becomes a white dwarf

24.2 Evolutionary stages of
medium mass stars

Figure 24.12 B

H-R diagram showing
stellar evolution

Figure 24.11

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Massive star
• Over 3 solar masses
• Short life span
• Terminates in a brilliant explosion called
a supernova
• Interior condenses
• May produce a hot, dense object that is
either a neutron star or a black hole

24.2 Evolutionary stages of
massive stars

Figure 24.12 C

24.2 Stellar remnants
 White
•
•

Small (some no larger than Earth)
Dense
•
•
•

•
•

dwarf

Can be more massive than the Sun
Spoonful weighs several tons
Atoms take up less space
• Electrons displaced inward
• Called degenerate matter

Hot surface
Cools to become a black dwarf

24.2 Stellar remnants (continued)
 Neutron
•

Forms from a more massive star
•
•

•
•

star

Star has more gravity
Squeezes itself smaller

Remnant of a supernova
Gravitational force collapses atoms
•
•

Electrons combine with protons to produce
neutrons
Small size

24.2 Stellar remnants (continued)
 Neutron
•

Pea size sample
•
•

•
•

star

Weighs 100 million tons
Same density as an atomic nucleus

Strong magnetic field
First one discovered in early 1970s
•
•

Pulsar (pulsating radio source)
Found in the Crab nebula (remnant of an A.D.
1054 supernova)

Crab Nebula in the
constellation Taurus

Figure 24.14

24.2 Stellar remnants (continued)
 Black
•
•

•

More dense than a neutron star
Intense surface gravity lets no light escape
As matter is pulled into it
•
•

•

hole

Becomes very hot
Emits x-rays

Likely candidate is Cygnus X-1, a strong xray source

Quiz Break

24.3 Galaxies
 Milky
•

Way galaxy

Structure
•
•

•
•

Determined by using radio telescopes
Large spiral galaxy
• About 100,000 light-years wide
• Thickness at the galactic nucleus is about
10,000 light-years
Three spiral arms of stars
Sun is 30,000 light-years from the center

Face-on view of the
Milk Way Galaxy

Figure 24.18 A

Edge-on view of the
Milk Way Galaxy

Figure 24.18 B

24.3 Galaxies (continued)
 Milky
•

Rotation
•
•
•

•

Way galaxy

Around the galactic nucleus
Outermost stars move the slowest
Sun rotates around the galactic nucleus once
about every 200 million years

Halo surrounds the galactic disk
•
•
•

Spherical
Very tenuous gas
Numerous globular clusters

24.3 Galaxies (continued)
 Other
•
•

galaxies

Existence was first proposed in mid-1700s
by Immanuel Kant
Four basic types of galaxies
•

Spiral galaxy
• Arms extending from nucleus
• About 30% of all galaxies
• Large diameter of 20,000 to 125,000 light
years
• Contains both young and old stars
• e.g., Milky Way

Great Galaxy, a spiral galaxy, in
the constellation Andromeda

Figure 24.20

24.3 Galaxies (continued)
 Other
•

galaxies

Four basic types of galaxies
•

•

Barred spiral galaxy
• Stars arranged in the shape of a bar
• Generally quite large
• About 10% of all galaxies
Elliptical galaxy
• Ellipsoidal shape
• About 60% of all galaxies
• Most are smaller than spiral galaxies;
however, they are also the largest known
galaxies

A barred spiral galaxy

Figure 24.22

24.3 Galaxies (continued)
 Other
•

galaxies

Four basic types of galaxies
•

Irregular galaxy
• Lacks symmetry
• About 10% of all galaxies
• Contains mostly young stars
• e.g., Magellanic Clouds

24.3 Galaxies (continued)
 Galactic
•
•
•

Group of galaxies
Some contain thousands of galaxies
Local Group
•
•

•

cluster

Our own group of galaxies
Contains at least 28 galaxies

Supercluster
•
•

Huge swarm of galaxies
May be the largest entity in the universe

Quiz Break

24.4 Red shifts
 Doppler
•

effect

Change in the wavelength of light emitted
by an object due to its motion
•

•

Movement away stretches the wavelength
• Longer wavelength
• Light appears redder
Movement toward “squeezes” the wavelength
• Shorter wavelength
• Light shifted toward the blue

24.4 Red shifts (continued)
 Doppler
•

effect

Amount of the Doppler shift indicates the
rate of movement
•
•

Large Doppler shift indicates a high velocity
Small Doppler shift indicates a lower velocity

 Expanding
•

universe

Most galaxies exhibit a red Doppler shift
•

Moving away

Raisin bread analogy of an
expanding universe

Figure 24.24

24.4 Red shifts (continued)
 Expanding
•

universe

Most galaxies exhibit a red Doppler shift
•

•
•
•

Far galaxies
• Exhibit the greatest shift
• Greater velocity
Discovered in 1929 by Edwin Hubble
Hubble's Law – the recessional speed of
galaxies is proportional to their distance
Accounts for red shifts

24.4 Big Bang theory
 Accounts

for galaxies moving away

from us
 Universe was once confined to a "ball"
that was
•
•

•

Supermassive
Dense
Hot

24.4 Big Bang theory (continued)
 Big

Bang marks the inception of the
universe
•
•

Occurred about 15 billion years ago
All matter and space was created

 Matter

is moving outward
 Fate of the universe
•

Two possibilities
•
•

Universe will last forever
Outward expansion sill stop and gravitational;
contraction will follow

24.4 Big Bang theory (continued)
 Fate
•

of the universe

Final fate depends on the average density
of the universe
•
•

If the density is more than the critical density,
then the universe would contract
Current estimates point to less then the critical
density and predict an ever-expanding, or
open, universe

Chapter 24Test Guidance
You will be responsible on the test for answering 3 of the following 6
questions.
1.

2.

3.
4.
5.
6.

What causes the difference between a star’s apparent
magnitude and it absolute magnitude.
List and explain the three factors that control the apparent
brightness of a star as seen from Earth.
Describe how binary stars are used to determine stellar mass.
List and describe the four basic types of galaxies.
What is Hubble’s Law, please explain in detail.
Briefly describe the Big Bang Theory (not the TV show).

End of Chapter 24


Slide 30

Lecture Outlines
PowerPoint

Chapter 24
Earth Science 11e
Tarbuck/Lutgens
Modified for educational
purposes only
By S. Koziol 12-8-2010

© 2006 Pearson Prentice Hall

Earth Science, 11e
Beyond Our
Solar System
Chapter 24

24.1 Properties of stars
 Distance
•
•

Measuring a star's distance can be very
difficult
Stellar parallax
•
•
•

•
•

Used for measuring distance to a star
Apparent shift in a star's position due to the
orbital motion of Earth
Measured as an angle
Near stars have the largest parallax
Largest parallax is less than one second of arc

24. 1 Properties of stars
(continued)

 Distance
•
•

Distances to the stars are very large
Units of measurement
•
•

•

Kilometers or astronomical units are too
cumbersome to use
Light-year is used most often
• Distance that light travels in 1 year
• One light-year is 9.5 trillion km (5.8 trillion
miles)

Other methods for measuring distance are
also used

24. 1 Properties of stars
(continued)

 Stellar
•

Controlled by three factors
•

•
•

•

brightness

Size
Temperature
Distance

Magnitude
•

Measure of a star's brightness

24.1 Properties of stars
(continued)

 Stellar
•

brightness

Magnitude
•

Two types of measurement
• Apparent magnitude
• Brightness when a star is viewed from
Earth
• Decreases with distance
• Numbers are used to designate
magnitudes - dim stars have large
numbers and negative numbers are also
used

24.1 Properties of stars
(continued)

 Stellar
•

brightness

Magnitude
•

Two types of measurement
• Absolute magnitude
• "True" or intrinsic brightness of a star
• Brightness at a standard distance of
32.6 light-years
• Most stars' absolute magnitudes are
between -5 and +15

24.1 Properties of stars
(continued)

 Color
•

Hot star
•

•
•

•

and temperature

Temperature above 30,000 K
Emits short-wavelength light
Appears blue

Cool star
•
•
•

Temperature less than 3000 K
Emits longer-wavelength light
Appears red

24.1 Properties of stars
(continued)

 Color
•

and temperature

Between 5000 and 6000 K
•
•

Stars appear yellow
e.g., Sun

 Binary
•

stars and stellar mass

Binary stars
•

Two stars orbiting one another
• Stars are held together by mutual
gravitation
• Both orbit around a common center of mass

24.1 Properties of stars (continued)
 Binary
•

Binary stars
•

•
•

•

stars and stellar mass

Visual binaries are resolved telescopically
More than 50% of the stars in the universe are
binary stars
Used to determine stellar mass

Stellar mass
•

Determined using binary stars – the center of
mass is closest to the most massive star

Binary stars
orbit each
other around
their common
center of
mass
Figure 24.4

24.1 Properties of stars (continued)
 Binary
•

stars and stellar mass

Stellar mass
•

Mass of most stars is between one-tenth and
fifty times the mass of the Sun

24.1 Hertzsprung-Russell
diagram
 Shows
•
•

the relation between stellar

Brightness (absolute magnitude) and
Temperature

 Diagram

is made by plotting (graphing)
each star's
•
•

Luminosity (brightness) and
Temperature

24.1 Hertzsprung-Russell
diagram (continued)
 Parts
•

Main-sequence stars
•

•
•

•

of an H-R diagram

90% of all stars
Band through the center of the H-R diagram
Sun is in the main-sequence

Giants (or red giants)
•
•
•

Very luminous
Large
Upper-right on the H-R diagram

24.1 Hertzsprung-Russell
diagram (continued)
 Parts
•

Giants (or red giants)
•

•

•

of an H-R diagram

Very large giants are called supergiants
Only a few percent of all stars

White dwarfs
•
•

•
•
•

Fainter than main-sequence stars
Small (approximate the size of Earth)
Lower-central area on the H-R diagram
Not all are white in color
Perhaps 10% of all stars

Idealized HertzsprungRussell diagram

Figure 24.5

Quiz Break

24.2 Variable stars
 Stars

that fluctuate in brightness
 Types of variable stars
•

Pulsating variables
•
•

•

Fluctuate regularly in brightness
Expand and contract in size

Eruptive variables
•
•
•

Explosive event
Sudden brightening
Called a nova

24.2 Interstellar matter
 Between

the stars is "the vacuum of

space"
 Nebula
•
•

Cloud of dust and gases
Two major types of nebulae
•

Bright nebula
• Glows if it close to a very hot star
• Two types of bright nebulae
• Emission nebula
• Reflection nebula

The Orion Nebula is a wellknown emission nebula

Figure 24.8

A faint blue reflection nebula in
the Pleiades star cluster

Figure 24.9

24.2 Interstellar matter (continued)
 Nebula
•

Two major types of nebulae
•

Dark nebula
• Not close to any bright star
• Appear dark
• Contains the material that forms stars and
planets

24.2 Stellar evolution
 Stars

exist because of gravity
 Two opposing forces in a star are
•
•

Gravity – contracts
Thermal nuclear energy – expands

 Stages
•

Birth
•

•
•
•
•

In dark, cool, interstellar clouds
Gravity contracts the cloud
Temperature rises
Radiates long-wavelength (red) light
Becomes a protostar

24.2 Stellar evolution (continued)
 Stages
•

Protostar
•
•
•

•
•
•
•

Gravitational contraction of gaseous cloud
continues
Core reaches 10 million K
Hydrogen nuclei fuse
• Become helium nuclei
• Process is called hydrogen burning
Energy is released
Outward pressure increases
Outward pressure balanced by gravity pulling in
Star becomes a stable main-sequence star

24.2 Stellar evolution (continued)
 Stages
•

Main-sequence stage
•

Stars age at different rates
• Massive stars use fuel faster and exist for
only a few million years
• Small stars use fuel slowly and exist for
perhaps hundreds of billions of years

•

90% of a star's life is in the main-sequence

24.2 Stellar evolution (continued)
 Stages
•

Red giant stage
•
•

•
•
•

Hydrogen burning migrates outward
Star's outer envelope expands
• Surface cools
• Surface becomes red
Core is collapsing as helium is converted to
carbon
Eventually all nuclear fuel is used
Gravity squeezes the star

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Low-mass star
• 0.5 solar mass
• Red giant collapses
• Becomes a white dwarf

24.2 Evolutionary stages of
low mass stars

Figure 24.12 A

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Medium-mass star
• Between 0.5 and 3 solar masses
• Red giant collapses
• Planetary nebula forms
• Becomes a white dwarf

24.2 Evolutionary stages of
medium mass stars

Figure 24.12 B

H-R diagram showing
stellar evolution

Figure 24.11

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Massive star
• Over 3 solar masses
• Short life span
• Terminates in a brilliant explosion called
a supernova
• Interior condenses
• May produce a hot, dense object that is
either a neutron star or a black hole

24.2 Evolutionary stages of
massive stars

Figure 24.12 C

24.2 Stellar remnants
 White
•
•

Small (some no larger than Earth)
Dense
•
•
•

•
•

dwarf

Can be more massive than the Sun
Spoonful weighs several tons
Atoms take up less space
• Electrons displaced inward
• Called degenerate matter

Hot surface
Cools to become a black dwarf

24.2 Stellar remnants (continued)
 Neutron
•

Forms from a more massive star
•
•

•
•

star

Star has more gravity
Squeezes itself smaller

Remnant of a supernova
Gravitational force collapses atoms
•
•

Electrons combine with protons to produce
neutrons
Small size

24.2 Stellar remnants (continued)
 Neutron
•

Pea size sample
•
•

•
•

star

Weighs 100 million tons
Same density as an atomic nucleus

Strong magnetic field
First one discovered in early 1970s
•
•

Pulsar (pulsating radio source)
Found in the Crab nebula (remnant of an A.D.
1054 supernova)

Crab Nebula in the
constellation Taurus

Figure 24.14

24.2 Stellar remnants (continued)
 Black
•
•

•

More dense than a neutron star
Intense surface gravity lets no light escape
As matter is pulled into it
•
•

•

hole

Becomes very hot
Emits x-rays

Likely candidate is Cygnus X-1, a strong xray source

Quiz Break

24.3 Galaxies
 Milky
•

Way galaxy

Structure
•
•

•
•

Determined by using radio telescopes
Large spiral galaxy
• About 100,000 light-years wide
• Thickness at the galactic nucleus is about
10,000 light-years
Three spiral arms of stars
Sun is 30,000 light-years from the center

Face-on view of the
Milk Way Galaxy

Figure 24.18 A

Edge-on view of the
Milk Way Galaxy

Figure 24.18 B

24.3 Galaxies (continued)
 Milky
•

Rotation
•
•
•

•

Way galaxy

Around the galactic nucleus
Outermost stars move the slowest
Sun rotates around the galactic nucleus once
about every 200 million years

Halo surrounds the galactic disk
•
•
•

Spherical
Very tenuous gas
Numerous globular clusters

24.3 Galaxies (continued)
 Other
•
•

galaxies

Existence was first proposed in mid-1700s
by Immanuel Kant
Four basic types of galaxies
•

Spiral galaxy
• Arms extending from nucleus
• About 30% of all galaxies
• Large diameter of 20,000 to 125,000 light
years
• Contains both young and old stars
• e.g., Milky Way

Great Galaxy, a spiral galaxy, in
the constellation Andromeda

Figure 24.20

24.3 Galaxies (continued)
 Other
•

galaxies

Four basic types of galaxies
•

•

Barred spiral galaxy
• Stars arranged in the shape of a bar
• Generally quite large
• About 10% of all galaxies
Elliptical galaxy
• Ellipsoidal shape
• About 60% of all galaxies
• Most are smaller than spiral galaxies;
however, they are also the largest known
galaxies

A barred spiral galaxy

Figure 24.22

24.3 Galaxies (continued)
 Other
•

galaxies

Four basic types of galaxies
•

Irregular galaxy
• Lacks symmetry
• About 10% of all galaxies
• Contains mostly young stars
• e.g., Magellanic Clouds

24.3 Galaxies (continued)
 Galactic
•
•
•

Group of galaxies
Some contain thousands of galaxies
Local Group
•
•

•

cluster

Our own group of galaxies
Contains at least 28 galaxies

Supercluster
•
•

Huge swarm of galaxies
May be the largest entity in the universe

Quiz Break

24.4 Red shifts
 Doppler
•

effect

Change in the wavelength of light emitted
by an object due to its motion
•

•

Movement away stretches the wavelength
• Longer wavelength
• Light appears redder
Movement toward “squeezes” the wavelength
• Shorter wavelength
• Light shifted toward the blue

24.4 Red shifts (continued)
 Doppler
•

effect

Amount of the Doppler shift indicates the
rate of movement
•
•

Large Doppler shift indicates a high velocity
Small Doppler shift indicates a lower velocity

 Expanding
•

universe

Most galaxies exhibit a red Doppler shift
•

Moving away

Raisin bread analogy of an
expanding universe

Figure 24.24

24.4 Red shifts (continued)
 Expanding
•

universe

Most galaxies exhibit a red Doppler shift
•

•
•
•

Far galaxies
• Exhibit the greatest shift
• Greater velocity
Discovered in 1929 by Edwin Hubble
Hubble's Law – the recessional speed of
galaxies is proportional to their distance
Accounts for red shifts

24.4 Big Bang theory
 Accounts

for galaxies moving away

from us
 Universe was once confined to a "ball"
that was
•
•

•

Supermassive
Dense
Hot

24.4 Big Bang theory (continued)
 Big

Bang marks the inception of the
universe
•
•

Occurred about 15 billion years ago
All matter and space was created

 Matter

is moving outward
 Fate of the universe
•

Two possibilities
•
•

Universe will last forever
Outward expansion sill stop and gravitational;
contraction will follow

24.4 Big Bang theory (continued)
 Fate
•

of the universe

Final fate depends on the average density
of the universe
•
•

If the density is more than the critical density,
then the universe would contract
Current estimates point to less then the critical
density and predict an ever-expanding, or
open, universe

Chapter 24Test Guidance
You will be responsible on the test for answering 3 of the following 6
questions.
1.

2.

3.
4.
5.
6.

What causes the difference between a star’s apparent
magnitude and it absolute magnitude.
List and explain the three factors that control the apparent
brightness of a star as seen from Earth.
Describe how binary stars are used to determine stellar mass.
List and describe the four basic types of galaxies.
What is Hubble’s Law, please explain in detail.
Briefly describe the Big Bang Theory (not the TV show).

End of Chapter 24


Slide 31

Lecture Outlines
PowerPoint

Chapter 24
Earth Science 11e
Tarbuck/Lutgens
Modified for educational
purposes only
By S. Koziol 12-8-2010

© 2006 Pearson Prentice Hall

Earth Science, 11e
Beyond Our
Solar System
Chapter 24

24.1 Properties of stars
 Distance
•
•

Measuring a star's distance can be very
difficult
Stellar parallax
•
•
•

•
•

Used for measuring distance to a star
Apparent shift in a star's position due to the
orbital motion of Earth
Measured as an angle
Near stars have the largest parallax
Largest parallax is less than one second of arc

24. 1 Properties of stars
(continued)

 Distance
•
•

Distances to the stars are very large
Units of measurement
•
•

•

Kilometers or astronomical units are too
cumbersome to use
Light-year is used most often
• Distance that light travels in 1 year
• One light-year is 9.5 trillion km (5.8 trillion
miles)

Other methods for measuring distance are
also used

24. 1 Properties of stars
(continued)

 Stellar
•

Controlled by three factors
•

•
•

•

brightness

Size
Temperature
Distance

Magnitude
•

Measure of a star's brightness

24.1 Properties of stars
(continued)

 Stellar
•

brightness

Magnitude
•

Two types of measurement
• Apparent magnitude
• Brightness when a star is viewed from
Earth
• Decreases with distance
• Numbers are used to designate
magnitudes - dim stars have large
numbers and negative numbers are also
used

24.1 Properties of stars
(continued)

 Stellar
•

brightness

Magnitude
•

Two types of measurement
• Absolute magnitude
• "True" or intrinsic brightness of a star
• Brightness at a standard distance of
32.6 light-years
• Most stars' absolute magnitudes are
between -5 and +15

24.1 Properties of stars
(continued)

 Color
•

Hot star
•

•
•

•

and temperature

Temperature above 30,000 K
Emits short-wavelength light
Appears blue

Cool star
•
•
•

Temperature less than 3000 K
Emits longer-wavelength light
Appears red

24.1 Properties of stars
(continued)

 Color
•

and temperature

Between 5000 and 6000 K
•
•

Stars appear yellow
e.g., Sun

 Binary
•

stars and stellar mass

Binary stars
•

Two stars orbiting one another
• Stars are held together by mutual
gravitation
• Both orbit around a common center of mass

24.1 Properties of stars (continued)
 Binary
•

Binary stars
•

•
•

•

stars and stellar mass

Visual binaries are resolved telescopically
More than 50% of the stars in the universe are
binary stars
Used to determine stellar mass

Stellar mass
•

Determined using binary stars – the center of
mass is closest to the most massive star

Binary stars
orbit each
other around
their common
center of
mass
Figure 24.4

24.1 Properties of stars (continued)
 Binary
•

stars and stellar mass

Stellar mass
•

Mass of most stars is between one-tenth and
fifty times the mass of the Sun

24.1 Hertzsprung-Russell
diagram
 Shows
•
•

the relation between stellar

Brightness (absolute magnitude) and
Temperature

 Diagram

is made by plotting (graphing)
each star's
•
•

Luminosity (brightness) and
Temperature

24.1 Hertzsprung-Russell
diagram (continued)
 Parts
•

Main-sequence stars
•

•
•

•

of an H-R diagram

90% of all stars
Band through the center of the H-R diagram
Sun is in the main-sequence

Giants (or red giants)
•
•
•

Very luminous
Large
Upper-right on the H-R diagram

24.1 Hertzsprung-Russell
diagram (continued)
 Parts
•

Giants (or red giants)
•

•

•

of an H-R diagram

Very large giants are called supergiants
Only a few percent of all stars

White dwarfs
•
•

•
•
•

Fainter than main-sequence stars
Small (approximate the size of Earth)
Lower-central area on the H-R diagram
Not all are white in color
Perhaps 10% of all stars

Idealized HertzsprungRussell diagram

Figure 24.5

Quiz Break

24.2 Variable stars
 Stars

that fluctuate in brightness
 Types of variable stars
•

Pulsating variables
•
•

•

Fluctuate regularly in brightness
Expand and contract in size

Eruptive variables
•
•
•

Explosive event
Sudden brightening
Called a nova

24.2 Interstellar matter
 Between

the stars is "the vacuum of

space"
 Nebula
•
•

Cloud of dust and gases
Two major types of nebulae
•

Bright nebula
• Glows if it close to a very hot star
• Two types of bright nebulae
• Emission nebula
• Reflection nebula

The Orion Nebula is a wellknown emission nebula

Figure 24.8

A faint blue reflection nebula in
the Pleiades star cluster

Figure 24.9

24.2 Interstellar matter (continued)
 Nebula
•

Two major types of nebulae
•

Dark nebula
• Not close to any bright star
• Appear dark
• Contains the material that forms stars and
planets

24.2 Stellar evolution
 Stars

exist because of gravity
 Two opposing forces in a star are
•
•

Gravity – contracts
Thermal nuclear energy – expands

 Stages
•

Birth
•

•
•
•
•

In dark, cool, interstellar clouds
Gravity contracts the cloud
Temperature rises
Radiates long-wavelength (red) light
Becomes a protostar

24.2 Stellar evolution (continued)
 Stages
•

Protostar
•
•
•

•
•
•
•

Gravitational contraction of gaseous cloud
continues
Core reaches 10 million K
Hydrogen nuclei fuse
• Become helium nuclei
• Process is called hydrogen burning
Energy is released
Outward pressure increases
Outward pressure balanced by gravity pulling in
Star becomes a stable main-sequence star

24.2 Stellar evolution (continued)
 Stages
•

Main-sequence stage
•

Stars age at different rates
• Massive stars use fuel faster and exist for
only a few million years
• Small stars use fuel slowly and exist for
perhaps hundreds of billions of years

•

90% of a star's life is in the main-sequence

24.2 Stellar evolution (continued)
 Stages
•

Red giant stage
•
•

•
•
•

Hydrogen burning migrates outward
Star's outer envelope expands
• Surface cools
• Surface becomes red
Core is collapsing as helium is converted to
carbon
Eventually all nuclear fuel is used
Gravity squeezes the star

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Low-mass star
• 0.5 solar mass
• Red giant collapses
• Becomes a white dwarf

24.2 Evolutionary stages of
low mass stars

Figure 24.12 A

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Medium-mass star
• Between 0.5 and 3 solar masses
• Red giant collapses
• Planetary nebula forms
• Becomes a white dwarf

24.2 Evolutionary stages of
medium mass stars

Figure 24.12 B

H-R diagram showing
stellar evolution

Figure 24.11

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Massive star
• Over 3 solar masses
• Short life span
• Terminates in a brilliant explosion called
a supernova
• Interior condenses
• May produce a hot, dense object that is
either a neutron star or a black hole

24.2 Evolutionary stages of
massive stars

Figure 24.12 C

24.2 Stellar remnants
 White
•
•

Small (some no larger than Earth)
Dense
•
•
•

•
•

dwarf

Can be more massive than the Sun
Spoonful weighs several tons
Atoms take up less space
• Electrons displaced inward
• Called degenerate matter

Hot surface
Cools to become a black dwarf

24.2 Stellar remnants (continued)
 Neutron
•

Forms from a more massive star
•
•

•
•

star

Star has more gravity
Squeezes itself smaller

Remnant of a supernova
Gravitational force collapses atoms
•
•

Electrons combine with protons to produce
neutrons
Small size

24.2 Stellar remnants (continued)
 Neutron
•

Pea size sample
•
•

•
•

star

Weighs 100 million tons
Same density as an atomic nucleus

Strong magnetic field
First one discovered in early 1970s
•
•

Pulsar (pulsating radio source)
Found in the Crab nebula (remnant of an A.D.
1054 supernova)

Crab Nebula in the
constellation Taurus

Figure 24.14

24.2 Stellar remnants (continued)
 Black
•
•

•

More dense than a neutron star
Intense surface gravity lets no light escape
As matter is pulled into it
•
•

•

hole

Becomes very hot
Emits x-rays

Likely candidate is Cygnus X-1, a strong xray source

Quiz Break

24.3 Galaxies
 Milky
•

Way galaxy

Structure
•
•

•
•

Determined by using radio telescopes
Large spiral galaxy
• About 100,000 light-years wide
• Thickness at the galactic nucleus is about
10,000 light-years
Three spiral arms of stars
Sun is 30,000 light-years from the center

Face-on view of the
Milk Way Galaxy

Figure 24.18 A

Edge-on view of the
Milk Way Galaxy

Figure 24.18 B

24.3 Galaxies (continued)
 Milky
•

Rotation
•
•
•

•

Way galaxy

Around the galactic nucleus
Outermost stars move the slowest
Sun rotates around the galactic nucleus once
about every 200 million years

Halo surrounds the galactic disk
•
•
•

Spherical
Very tenuous gas
Numerous globular clusters

24.3 Galaxies (continued)
 Other
•
•

galaxies

Existence was first proposed in mid-1700s
by Immanuel Kant
Four basic types of galaxies
•

Spiral galaxy
• Arms extending from nucleus
• About 30% of all galaxies
• Large diameter of 20,000 to 125,000 light
years
• Contains both young and old stars
• e.g., Milky Way

Great Galaxy, a spiral galaxy, in
the constellation Andromeda

Figure 24.20

24.3 Galaxies (continued)
 Other
•

galaxies

Four basic types of galaxies
•

•

Barred spiral galaxy
• Stars arranged in the shape of a bar
• Generally quite large
• About 10% of all galaxies
Elliptical galaxy
• Ellipsoidal shape
• About 60% of all galaxies
• Most are smaller than spiral galaxies;
however, they are also the largest known
galaxies

A barred spiral galaxy

Figure 24.22

24.3 Galaxies (continued)
 Other
•

galaxies

Four basic types of galaxies
•

Irregular galaxy
• Lacks symmetry
• About 10% of all galaxies
• Contains mostly young stars
• e.g., Magellanic Clouds

24.3 Galaxies (continued)
 Galactic
•
•
•

Group of galaxies
Some contain thousands of galaxies
Local Group
•
•

•

cluster

Our own group of galaxies
Contains at least 28 galaxies

Supercluster
•
•

Huge swarm of galaxies
May be the largest entity in the universe

Quiz Break

24.4 Red shifts
 Doppler
•

effect

Change in the wavelength of light emitted
by an object due to its motion
•

•

Movement away stretches the wavelength
• Longer wavelength
• Light appears redder
Movement toward “squeezes” the wavelength
• Shorter wavelength
• Light shifted toward the blue

24.4 Red shifts (continued)
 Doppler
•

effect

Amount of the Doppler shift indicates the
rate of movement
•
•

Large Doppler shift indicates a high velocity
Small Doppler shift indicates a lower velocity

 Expanding
•

universe

Most galaxies exhibit a red Doppler shift
•

Moving away

Raisin bread analogy of an
expanding universe

Figure 24.24

24.4 Red shifts (continued)
 Expanding
•

universe

Most galaxies exhibit a red Doppler shift
•

•
•
•

Far galaxies
• Exhibit the greatest shift
• Greater velocity
Discovered in 1929 by Edwin Hubble
Hubble's Law – the recessional speed of
galaxies is proportional to their distance
Accounts for red shifts

24.4 Big Bang theory
 Accounts

for galaxies moving away

from us
 Universe was once confined to a "ball"
that was
•
•

•

Supermassive
Dense
Hot

24.4 Big Bang theory (continued)
 Big

Bang marks the inception of the
universe
•
•

Occurred about 15 billion years ago
All matter and space was created

 Matter

is moving outward
 Fate of the universe
•

Two possibilities
•
•

Universe will last forever
Outward expansion sill stop and gravitational;
contraction will follow

24.4 Big Bang theory (continued)
 Fate
•

of the universe

Final fate depends on the average density
of the universe
•
•

If the density is more than the critical density,
then the universe would contract
Current estimates point to less then the critical
density and predict an ever-expanding, or
open, universe

Chapter 24Test Guidance
You will be responsible on the test for answering 3 of the following 6
questions.
1.

2.

3.
4.
5.
6.

What causes the difference between a star’s apparent
magnitude and it absolute magnitude.
List and explain the three factors that control the apparent
brightness of a star as seen from Earth.
Describe how binary stars are used to determine stellar mass.
List and describe the four basic types of galaxies.
What is Hubble’s Law, please explain in detail.
Briefly describe the Big Bang Theory (not the TV show).

End of Chapter 24


Slide 32

Lecture Outlines
PowerPoint

Chapter 24
Earth Science 11e
Tarbuck/Lutgens
Modified for educational
purposes only
By S. Koziol 12-8-2010

© 2006 Pearson Prentice Hall

Earth Science, 11e
Beyond Our
Solar System
Chapter 24

24.1 Properties of stars
 Distance
•
•

Measuring a star's distance can be very
difficult
Stellar parallax
•
•
•

•
•

Used for measuring distance to a star
Apparent shift in a star's position due to the
orbital motion of Earth
Measured as an angle
Near stars have the largest parallax
Largest parallax is less than one second of arc

24. 1 Properties of stars
(continued)

 Distance
•
•

Distances to the stars are very large
Units of measurement
•
•

•

Kilometers or astronomical units are too
cumbersome to use
Light-year is used most often
• Distance that light travels in 1 year
• One light-year is 9.5 trillion km (5.8 trillion
miles)

Other methods for measuring distance are
also used

24. 1 Properties of stars
(continued)

 Stellar
•

Controlled by three factors
•

•
•

•

brightness

Size
Temperature
Distance

Magnitude
•

Measure of a star's brightness

24.1 Properties of stars
(continued)

 Stellar
•

brightness

Magnitude
•

Two types of measurement
• Apparent magnitude
• Brightness when a star is viewed from
Earth
• Decreases with distance
• Numbers are used to designate
magnitudes - dim stars have large
numbers and negative numbers are also
used

24.1 Properties of stars
(continued)

 Stellar
•

brightness

Magnitude
•

Two types of measurement
• Absolute magnitude
• "True" or intrinsic brightness of a star
• Brightness at a standard distance of
32.6 light-years
• Most stars' absolute magnitudes are
between -5 and +15

24.1 Properties of stars
(continued)

 Color
•

Hot star
•

•
•

•

and temperature

Temperature above 30,000 K
Emits short-wavelength light
Appears blue

Cool star
•
•
•

Temperature less than 3000 K
Emits longer-wavelength light
Appears red

24.1 Properties of stars
(continued)

 Color
•

and temperature

Between 5000 and 6000 K
•
•

Stars appear yellow
e.g., Sun

 Binary
•

stars and stellar mass

Binary stars
•

Two stars orbiting one another
• Stars are held together by mutual
gravitation
• Both orbit around a common center of mass

24.1 Properties of stars (continued)
 Binary
•

Binary stars
•

•
•

•

stars and stellar mass

Visual binaries are resolved telescopically
More than 50% of the stars in the universe are
binary stars
Used to determine stellar mass

Stellar mass
•

Determined using binary stars – the center of
mass is closest to the most massive star

Binary stars
orbit each
other around
their common
center of
mass
Figure 24.4

24.1 Properties of stars (continued)
 Binary
•

stars and stellar mass

Stellar mass
•

Mass of most stars is between one-tenth and
fifty times the mass of the Sun

24.1 Hertzsprung-Russell
diagram
 Shows
•
•

the relation between stellar

Brightness (absolute magnitude) and
Temperature

 Diagram

is made by plotting (graphing)
each star's
•
•

Luminosity (brightness) and
Temperature

24.1 Hertzsprung-Russell
diagram (continued)
 Parts
•

Main-sequence stars
•

•
•

•

of an H-R diagram

90% of all stars
Band through the center of the H-R diagram
Sun is in the main-sequence

Giants (or red giants)
•
•
•

Very luminous
Large
Upper-right on the H-R diagram

24.1 Hertzsprung-Russell
diagram (continued)
 Parts
•

Giants (or red giants)
•

•

•

of an H-R diagram

Very large giants are called supergiants
Only a few percent of all stars

White dwarfs
•
•

•
•
•

Fainter than main-sequence stars
Small (approximate the size of Earth)
Lower-central area on the H-R diagram
Not all are white in color
Perhaps 10% of all stars

Idealized HertzsprungRussell diagram

Figure 24.5

Quiz Break

24.2 Variable stars
 Stars

that fluctuate in brightness
 Types of variable stars
•

Pulsating variables
•
•

•

Fluctuate regularly in brightness
Expand and contract in size

Eruptive variables
•
•
•

Explosive event
Sudden brightening
Called a nova

24.2 Interstellar matter
 Between

the stars is "the vacuum of

space"
 Nebula
•
•

Cloud of dust and gases
Two major types of nebulae
•

Bright nebula
• Glows if it close to a very hot star
• Two types of bright nebulae
• Emission nebula
• Reflection nebula

The Orion Nebula is a wellknown emission nebula

Figure 24.8

A faint blue reflection nebula in
the Pleiades star cluster

Figure 24.9

24.2 Interstellar matter (continued)
 Nebula
•

Two major types of nebulae
•

Dark nebula
• Not close to any bright star
• Appear dark
• Contains the material that forms stars and
planets

24.2 Stellar evolution
 Stars

exist because of gravity
 Two opposing forces in a star are
•
•

Gravity – contracts
Thermal nuclear energy – expands

 Stages
•

Birth
•

•
•
•
•

In dark, cool, interstellar clouds
Gravity contracts the cloud
Temperature rises
Radiates long-wavelength (red) light
Becomes a protostar

24.2 Stellar evolution (continued)
 Stages
•

Protostar
•
•
•

•
•
•
•

Gravitational contraction of gaseous cloud
continues
Core reaches 10 million K
Hydrogen nuclei fuse
• Become helium nuclei
• Process is called hydrogen burning
Energy is released
Outward pressure increases
Outward pressure balanced by gravity pulling in
Star becomes a stable main-sequence star

24.2 Stellar evolution (continued)
 Stages
•

Main-sequence stage
•

Stars age at different rates
• Massive stars use fuel faster and exist for
only a few million years
• Small stars use fuel slowly and exist for
perhaps hundreds of billions of years

•

90% of a star's life is in the main-sequence

24.2 Stellar evolution (continued)
 Stages
•

Red giant stage
•
•

•
•
•

Hydrogen burning migrates outward
Star's outer envelope expands
• Surface cools
• Surface becomes red
Core is collapsing as helium is converted to
carbon
Eventually all nuclear fuel is used
Gravity squeezes the star

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Low-mass star
• 0.5 solar mass
• Red giant collapses
• Becomes a white dwarf

24.2 Evolutionary stages of
low mass stars

Figure 24.12 A

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Medium-mass star
• Between 0.5 and 3 solar masses
• Red giant collapses
• Planetary nebula forms
• Becomes a white dwarf

24.2 Evolutionary stages of
medium mass stars

Figure 24.12 B

H-R diagram showing
stellar evolution

Figure 24.11

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Massive star
• Over 3 solar masses
• Short life span
• Terminates in a brilliant explosion called
a supernova
• Interior condenses
• May produce a hot, dense object that is
either a neutron star or a black hole

24.2 Evolutionary stages of
massive stars

Figure 24.12 C

24.2 Stellar remnants
 White
•
•

Small (some no larger than Earth)
Dense
•
•
•

•
•

dwarf

Can be more massive than the Sun
Spoonful weighs several tons
Atoms take up less space
• Electrons displaced inward
• Called degenerate matter

Hot surface
Cools to become a black dwarf

24.2 Stellar remnants (continued)
 Neutron
•

Forms from a more massive star
•
•

•
•

star

Star has more gravity
Squeezes itself smaller

Remnant of a supernova
Gravitational force collapses atoms
•
•

Electrons combine with protons to produce
neutrons
Small size

24.2 Stellar remnants (continued)
 Neutron
•

Pea size sample
•
•

•
•

star

Weighs 100 million tons
Same density as an atomic nucleus

Strong magnetic field
First one discovered in early 1970s
•
•

Pulsar (pulsating radio source)
Found in the Crab nebula (remnant of an A.D.
1054 supernova)

Crab Nebula in the
constellation Taurus

Figure 24.14

24.2 Stellar remnants (continued)
 Black
•
•

•

More dense than a neutron star
Intense surface gravity lets no light escape
As matter is pulled into it
•
•

•

hole

Becomes very hot
Emits x-rays

Likely candidate is Cygnus X-1, a strong xray source

Quiz Break

24.3 Galaxies
 Milky
•

Way galaxy

Structure
•
•

•
•

Determined by using radio telescopes
Large spiral galaxy
• About 100,000 light-years wide
• Thickness at the galactic nucleus is about
10,000 light-years
Three spiral arms of stars
Sun is 30,000 light-years from the center

Face-on view of the
Milk Way Galaxy

Figure 24.18 A

Edge-on view of the
Milk Way Galaxy

Figure 24.18 B

24.3 Galaxies (continued)
 Milky
•

Rotation
•
•
•

•

Way galaxy

Around the galactic nucleus
Outermost stars move the slowest
Sun rotates around the galactic nucleus once
about every 200 million years

Halo surrounds the galactic disk
•
•
•

Spherical
Very tenuous gas
Numerous globular clusters

24.3 Galaxies (continued)
 Other
•
•

galaxies

Existence was first proposed in mid-1700s
by Immanuel Kant
Four basic types of galaxies
•

Spiral galaxy
• Arms extending from nucleus
• About 30% of all galaxies
• Large diameter of 20,000 to 125,000 light
years
• Contains both young and old stars
• e.g., Milky Way

Great Galaxy, a spiral galaxy, in
the constellation Andromeda

Figure 24.20

24.3 Galaxies (continued)
 Other
•

galaxies

Four basic types of galaxies
•

•

Barred spiral galaxy
• Stars arranged in the shape of a bar
• Generally quite large
• About 10% of all galaxies
Elliptical galaxy
• Ellipsoidal shape
• About 60% of all galaxies
• Most are smaller than spiral galaxies;
however, they are also the largest known
galaxies

A barred spiral galaxy

Figure 24.22

24.3 Galaxies (continued)
 Other
•

galaxies

Four basic types of galaxies
•

Irregular galaxy
• Lacks symmetry
• About 10% of all galaxies
• Contains mostly young stars
• e.g., Magellanic Clouds

24.3 Galaxies (continued)
 Galactic
•
•
•

Group of galaxies
Some contain thousands of galaxies
Local Group
•
•

•

cluster

Our own group of galaxies
Contains at least 28 galaxies

Supercluster
•
•

Huge swarm of galaxies
May be the largest entity in the universe

Quiz Break

24.4 Red shifts
 Doppler
•

effect

Change in the wavelength of light emitted
by an object due to its motion
•

•

Movement away stretches the wavelength
• Longer wavelength
• Light appears redder
Movement toward “squeezes” the wavelength
• Shorter wavelength
• Light shifted toward the blue

24.4 Red shifts (continued)
 Doppler
•

effect

Amount of the Doppler shift indicates the
rate of movement
•
•

Large Doppler shift indicates a high velocity
Small Doppler shift indicates a lower velocity

 Expanding
•

universe

Most galaxies exhibit a red Doppler shift
•

Moving away

Raisin bread analogy of an
expanding universe

Figure 24.24

24.4 Red shifts (continued)
 Expanding
•

universe

Most galaxies exhibit a red Doppler shift
•

•
•
•

Far galaxies
• Exhibit the greatest shift
• Greater velocity
Discovered in 1929 by Edwin Hubble
Hubble's Law – the recessional speed of
galaxies is proportional to their distance
Accounts for red shifts

24.4 Big Bang theory
 Accounts

for galaxies moving away

from us
 Universe was once confined to a "ball"
that was
•
•

•

Supermassive
Dense
Hot

24.4 Big Bang theory (continued)
 Big

Bang marks the inception of the
universe
•
•

Occurred about 15 billion years ago
All matter and space was created

 Matter

is moving outward
 Fate of the universe
•

Two possibilities
•
•

Universe will last forever
Outward expansion sill stop and gravitational;
contraction will follow

24.4 Big Bang theory (continued)
 Fate
•

of the universe

Final fate depends on the average density
of the universe
•
•

If the density is more than the critical density,
then the universe would contract
Current estimates point to less then the critical
density and predict an ever-expanding, or
open, universe

Chapter 24Test Guidance
You will be responsible on the test for answering 3 of the following 6
questions.
1.

2.

3.
4.
5.
6.

What causes the difference between a star’s apparent
magnitude and it absolute magnitude.
List and explain the three factors that control the apparent
brightness of a star as seen from Earth.
Describe how binary stars are used to determine stellar mass.
List and describe the four basic types of galaxies.
What is Hubble’s Law, please explain in detail.
Briefly describe the Big Bang Theory (not the TV show).

End of Chapter 24


Slide 33

Lecture Outlines
PowerPoint

Chapter 24
Earth Science 11e
Tarbuck/Lutgens
Modified for educational
purposes only
By S. Koziol 12-8-2010

© 2006 Pearson Prentice Hall

Earth Science, 11e
Beyond Our
Solar System
Chapter 24

24.1 Properties of stars
 Distance
•
•

Measuring a star's distance can be very
difficult
Stellar parallax
•
•
•

•
•

Used for measuring distance to a star
Apparent shift in a star's position due to the
orbital motion of Earth
Measured as an angle
Near stars have the largest parallax
Largest parallax is less than one second of arc

24. 1 Properties of stars
(continued)

 Distance
•
•

Distances to the stars are very large
Units of measurement
•
•

•

Kilometers or astronomical units are too
cumbersome to use
Light-year is used most often
• Distance that light travels in 1 year
• One light-year is 9.5 trillion km (5.8 trillion
miles)

Other methods for measuring distance are
also used

24. 1 Properties of stars
(continued)

 Stellar
•

Controlled by three factors
•

•
•

•

brightness

Size
Temperature
Distance

Magnitude
•

Measure of a star's brightness

24.1 Properties of stars
(continued)

 Stellar
•

brightness

Magnitude
•

Two types of measurement
• Apparent magnitude
• Brightness when a star is viewed from
Earth
• Decreases with distance
• Numbers are used to designate
magnitudes - dim stars have large
numbers and negative numbers are also
used

24.1 Properties of stars
(continued)

 Stellar
•

brightness

Magnitude
•

Two types of measurement
• Absolute magnitude
• "True" or intrinsic brightness of a star
• Brightness at a standard distance of
32.6 light-years
• Most stars' absolute magnitudes are
between -5 and +15

24.1 Properties of stars
(continued)

 Color
•

Hot star
•

•
•

•

and temperature

Temperature above 30,000 K
Emits short-wavelength light
Appears blue

Cool star
•
•
•

Temperature less than 3000 K
Emits longer-wavelength light
Appears red

24.1 Properties of stars
(continued)

 Color
•

and temperature

Between 5000 and 6000 K
•
•

Stars appear yellow
e.g., Sun

 Binary
•

stars and stellar mass

Binary stars
•

Two stars orbiting one another
• Stars are held together by mutual
gravitation
• Both orbit around a common center of mass

24.1 Properties of stars (continued)
 Binary
•

Binary stars
•

•
•

•

stars and stellar mass

Visual binaries are resolved telescopically
More than 50% of the stars in the universe are
binary stars
Used to determine stellar mass

Stellar mass
•

Determined using binary stars – the center of
mass is closest to the most massive star

Binary stars
orbit each
other around
their common
center of
mass
Figure 24.4

24.1 Properties of stars (continued)
 Binary
•

stars and stellar mass

Stellar mass
•

Mass of most stars is between one-tenth and
fifty times the mass of the Sun

24.1 Hertzsprung-Russell
diagram
 Shows
•
•

the relation between stellar

Brightness (absolute magnitude) and
Temperature

 Diagram

is made by plotting (graphing)
each star's
•
•

Luminosity (brightness) and
Temperature

24.1 Hertzsprung-Russell
diagram (continued)
 Parts
•

Main-sequence stars
•

•
•

•

of an H-R diagram

90% of all stars
Band through the center of the H-R diagram
Sun is in the main-sequence

Giants (or red giants)
•
•
•

Very luminous
Large
Upper-right on the H-R diagram

24.1 Hertzsprung-Russell
diagram (continued)
 Parts
•

Giants (or red giants)
•

•

•

of an H-R diagram

Very large giants are called supergiants
Only a few percent of all stars

White dwarfs
•
•

•
•
•

Fainter than main-sequence stars
Small (approximate the size of Earth)
Lower-central area on the H-R diagram
Not all are white in color
Perhaps 10% of all stars

Idealized HertzsprungRussell diagram

Figure 24.5

Quiz Break

24.2 Variable stars
 Stars

that fluctuate in brightness
 Types of variable stars
•

Pulsating variables
•
•

•

Fluctuate regularly in brightness
Expand and contract in size

Eruptive variables
•
•
•

Explosive event
Sudden brightening
Called a nova

24.2 Interstellar matter
 Between

the stars is "the vacuum of

space"
 Nebula
•
•

Cloud of dust and gases
Two major types of nebulae
•

Bright nebula
• Glows if it close to a very hot star
• Two types of bright nebulae
• Emission nebula
• Reflection nebula

The Orion Nebula is a wellknown emission nebula

Figure 24.8

A faint blue reflection nebula in
the Pleiades star cluster

Figure 24.9

24.2 Interstellar matter (continued)
 Nebula
•

Two major types of nebulae
•

Dark nebula
• Not close to any bright star
• Appear dark
• Contains the material that forms stars and
planets

24.2 Stellar evolution
 Stars

exist because of gravity
 Two opposing forces in a star are
•
•

Gravity – contracts
Thermal nuclear energy – expands

 Stages
•

Birth
•

•
•
•
•

In dark, cool, interstellar clouds
Gravity contracts the cloud
Temperature rises
Radiates long-wavelength (red) light
Becomes a protostar

24.2 Stellar evolution (continued)
 Stages
•

Protostar
•
•
•

•
•
•
•

Gravitational contraction of gaseous cloud
continues
Core reaches 10 million K
Hydrogen nuclei fuse
• Become helium nuclei
• Process is called hydrogen burning
Energy is released
Outward pressure increases
Outward pressure balanced by gravity pulling in
Star becomes a stable main-sequence star

24.2 Stellar evolution (continued)
 Stages
•

Main-sequence stage
•

Stars age at different rates
• Massive stars use fuel faster and exist for
only a few million years
• Small stars use fuel slowly and exist for
perhaps hundreds of billions of years

•

90% of a star's life is in the main-sequence

24.2 Stellar evolution (continued)
 Stages
•

Red giant stage
•
•

•
•
•

Hydrogen burning migrates outward
Star's outer envelope expands
• Surface cools
• Surface becomes red
Core is collapsing as helium is converted to
carbon
Eventually all nuclear fuel is used
Gravity squeezes the star

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Low-mass star
• 0.5 solar mass
• Red giant collapses
• Becomes a white dwarf

24.2 Evolutionary stages of
low mass stars

Figure 24.12 A

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Medium-mass star
• Between 0.5 and 3 solar masses
• Red giant collapses
• Planetary nebula forms
• Becomes a white dwarf

24.2 Evolutionary stages of
medium mass stars

Figure 24.12 B

H-R diagram showing
stellar evolution

Figure 24.11

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Massive star
• Over 3 solar masses
• Short life span
• Terminates in a brilliant explosion called
a supernova
• Interior condenses
• May produce a hot, dense object that is
either a neutron star or a black hole

24.2 Evolutionary stages of
massive stars

Figure 24.12 C

24.2 Stellar remnants
 White
•
•

Small (some no larger than Earth)
Dense
•
•
•

•
•

dwarf

Can be more massive than the Sun
Spoonful weighs several tons
Atoms take up less space
• Electrons displaced inward
• Called degenerate matter

Hot surface
Cools to become a black dwarf

24.2 Stellar remnants (continued)
 Neutron
•

Forms from a more massive star
•
•

•
•

star

Star has more gravity
Squeezes itself smaller

Remnant of a supernova
Gravitational force collapses atoms
•
•

Electrons combine with protons to produce
neutrons
Small size

24.2 Stellar remnants (continued)
 Neutron
•

Pea size sample
•
•

•
•

star

Weighs 100 million tons
Same density as an atomic nucleus

Strong magnetic field
First one discovered in early 1970s
•
•

Pulsar (pulsating radio source)
Found in the Crab nebula (remnant of an A.D.
1054 supernova)

Crab Nebula in the
constellation Taurus

Figure 24.14

24.2 Stellar remnants (continued)
 Black
•
•

•

More dense than a neutron star
Intense surface gravity lets no light escape
As matter is pulled into it
•
•

•

hole

Becomes very hot
Emits x-rays

Likely candidate is Cygnus X-1, a strong xray source

Quiz Break

24.3 Galaxies
 Milky
•

Way galaxy

Structure
•
•

•
•

Determined by using radio telescopes
Large spiral galaxy
• About 100,000 light-years wide
• Thickness at the galactic nucleus is about
10,000 light-years
Three spiral arms of stars
Sun is 30,000 light-years from the center

Face-on view of the
Milk Way Galaxy

Figure 24.18 A

Edge-on view of the
Milk Way Galaxy

Figure 24.18 B

24.3 Galaxies (continued)
 Milky
•

Rotation
•
•
•

•

Way galaxy

Around the galactic nucleus
Outermost stars move the slowest
Sun rotates around the galactic nucleus once
about every 200 million years

Halo surrounds the galactic disk
•
•
•

Spherical
Very tenuous gas
Numerous globular clusters

24.3 Galaxies (continued)
 Other
•
•

galaxies

Existence was first proposed in mid-1700s
by Immanuel Kant
Four basic types of galaxies
•

Spiral galaxy
• Arms extending from nucleus
• About 30% of all galaxies
• Large diameter of 20,000 to 125,000 light
years
• Contains both young and old stars
• e.g., Milky Way

Great Galaxy, a spiral galaxy, in
the constellation Andromeda

Figure 24.20

24.3 Galaxies (continued)
 Other
•

galaxies

Four basic types of galaxies
•

•

Barred spiral galaxy
• Stars arranged in the shape of a bar
• Generally quite large
• About 10% of all galaxies
Elliptical galaxy
• Ellipsoidal shape
• About 60% of all galaxies
• Most are smaller than spiral galaxies;
however, they are also the largest known
galaxies

A barred spiral galaxy

Figure 24.22

24.3 Galaxies (continued)
 Other
•

galaxies

Four basic types of galaxies
•

Irregular galaxy
• Lacks symmetry
• About 10% of all galaxies
• Contains mostly young stars
• e.g., Magellanic Clouds

24.3 Galaxies (continued)
 Galactic
•
•
•

Group of galaxies
Some contain thousands of galaxies
Local Group
•
•

•

cluster

Our own group of galaxies
Contains at least 28 galaxies

Supercluster
•
•

Huge swarm of galaxies
May be the largest entity in the universe

Quiz Break

24.4 Red shifts
 Doppler
•

effect

Change in the wavelength of light emitted
by an object due to its motion
•

•

Movement away stretches the wavelength
• Longer wavelength
• Light appears redder
Movement toward “squeezes” the wavelength
• Shorter wavelength
• Light shifted toward the blue

24.4 Red shifts (continued)
 Doppler
•

effect

Amount of the Doppler shift indicates the
rate of movement
•
•

Large Doppler shift indicates a high velocity
Small Doppler shift indicates a lower velocity

 Expanding
•

universe

Most galaxies exhibit a red Doppler shift
•

Moving away

Raisin bread analogy of an
expanding universe

Figure 24.24

24.4 Red shifts (continued)
 Expanding
•

universe

Most galaxies exhibit a red Doppler shift
•

•
•
•

Far galaxies
• Exhibit the greatest shift
• Greater velocity
Discovered in 1929 by Edwin Hubble
Hubble's Law – the recessional speed of
galaxies is proportional to their distance
Accounts for red shifts

24.4 Big Bang theory
 Accounts

for galaxies moving away

from us
 Universe was once confined to a "ball"
that was
•
•

•

Supermassive
Dense
Hot

24.4 Big Bang theory (continued)
 Big

Bang marks the inception of the
universe
•
•

Occurred about 15 billion years ago
All matter and space was created

 Matter

is moving outward
 Fate of the universe
•

Two possibilities
•
•

Universe will last forever
Outward expansion sill stop and gravitational;
contraction will follow

24.4 Big Bang theory (continued)
 Fate
•

of the universe

Final fate depends on the average density
of the universe
•
•

If the density is more than the critical density,
then the universe would contract
Current estimates point to less then the critical
density and predict an ever-expanding, or
open, universe

Chapter 24Test Guidance
You will be responsible on the test for answering 3 of the following 6
questions.
1.

2.

3.
4.
5.
6.

What causes the difference between a star’s apparent
magnitude and it absolute magnitude.
List and explain the three factors that control the apparent
brightness of a star as seen from Earth.
Describe how binary stars are used to determine stellar mass.
List and describe the four basic types of galaxies.
What is Hubble’s Law, please explain in detail.
Briefly describe the Big Bang Theory (not the TV show).

End of Chapter 24


Slide 34

Lecture Outlines
PowerPoint

Chapter 24
Earth Science 11e
Tarbuck/Lutgens
Modified for educational
purposes only
By S. Koziol 12-8-2010

© 2006 Pearson Prentice Hall

Earth Science, 11e
Beyond Our
Solar System
Chapter 24

24.1 Properties of stars
 Distance
•
•

Measuring a star's distance can be very
difficult
Stellar parallax
•
•
•

•
•

Used for measuring distance to a star
Apparent shift in a star's position due to the
orbital motion of Earth
Measured as an angle
Near stars have the largest parallax
Largest parallax is less than one second of arc

24. 1 Properties of stars
(continued)

 Distance
•
•

Distances to the stars are very large
Units of measurement
•
•

•

Kilometers or astronomical units are too
cumbersome to use
Light-year is used most often
• Distance that light travels in 1 year
• One light-year is 9.5 trillion km (5.8 trillion
miles)

Other methods for measuring distance are
also used

24. 1 Properties of stars
(continued)

 Stellar
•

Controlled by three factors
•

•
•

•

brightness

Size
Temperature
Distance

Magnitude
•

Measure of a star's brightness

24.1 Properties of stars
(continued)

 Stellar
•

brightness

Magnitude
•

Two types of measurement
• Apparent magnitude
• Brightness when a star is viewed from
Earth
• Decreases with distance
• Numbers are used to designate
magnitudes - dim stars have large
numbers and negative numbers are also
used

24.1 Properties of stars
(continued)

 Stellar
•

brightness

Magnitude
•

Two types of measurement
• Absolute magnitude
• "True" or intrinsic brightness of a star
• Brightness at a standard distance of
32.6 light-years
• Most stars' absolute magnitudes are
between -5 and +15

24.1 Properties of stars
(continued)

 Color
•

Hot star
•

•
•

•

and temperature

Temperature above 30,000 K
Emits short-wavelength light
Appears blue

Cool star
•
•
•

Temperature less than 3000 K
Emits longer-wavelength light
Appears red

24.1 Properties of stars
(continued)

 Color
•

and temperature

Between 5000 and 6000 K
•
•

Stars appear yellow
e.g., Sun

 Binary
•

stars and stellar mass

Binary stars
•

Two stars orbiting one another
• Stars are held together by mutual
gravitation
• Both orbit around a common center of mass

24.1 Properties of stars (continued)
 Binary
•

Binary stars
•

•
•

•

stars and stellar mass

Visual binaries are resolved telescopically
More than 50% of the stars in the universe are
binary stars
Used to determine stellar mass

Stellar mass
•

Determined using binary stars – the center of
mass is closest to the most massive star

Binary stars
orbit each
other around
their common
center of
mass
Figure 24.4

24.1 Properties of stars (continued)
 Binary
•

stars and stellar mass

Stellar mass
•

Mass of most stars is between one-tenth and
fifty times the mass of the Sun

24.1 Hertzsprung-Russell
diagram
 Shows
•
•

the relation between stellar

Brightness (absolute magnitude) and
Temperature

 Diagram

is made by plotting (graphing)
each star's
•
•

Luminosity (brightness) and
Temperature

24.1 Hertzsprung-Russell
diagram (continued)
 Parts
•

Main-sequence stars
•

•
•

•

of an H-R diagram

90% of all stars
Band through the center of the H-R diagram
Sun is in the main-sequence

Giants (or red giants)
•
•
•

Very luminous
Large
Upper-right on the H-R diagram

24.1 Hertzsprung-Russell
diagram (continued)
 Parts
•

Giants (or red giants)
•

•

•

of an H-R diagram

Very large giants are called supergiants
Only a few percent of all stars

White dwarfs
•
•

•
•
•

Fainter than main-sequence stars
Small (approximate the size of Earth)
Lower-central area on the H-R diagram
Not all are white in color
Perhaps 10% of all stars

Idealized HertzsprungRussell diagram

Figure 24.5

Quiz Break

24.2 Variable stars
 Stars

that fluctuate in brightness
 Types of variable stars
•

Pulsating variables
•
•

•

Fluctuate regularly in brightness
Expand and contract in size

Eruptive variables
•
•
•

Explosive event
Sudden brightening
Called a nova

24.2 Interstellar matter
 Between

the stars is "the vacuum of

space"
 Nebula
•
•

Cloud of dust and gases
Two major types of nebulae
•

Bright nebula
• Glows if it close to a very hot star
• Two types of bright nebulae
• Emission nebula
• Reflection nebula

The Orion Nebula is a wellknown emission nebula

Figure 24.8

A faint blue reflection nebula in
the Pleiades star cluster

Figure 24.9

24.2 Interstellar matter (continued)
 Nebula
•

Two major types of nebulae
•

Dark nebula
• Not close to any bright star
• Appear dark
• Contains the material that forms stars and
planets

24.2 Stellar evolution
 Stars

exist because of gravity
 Two opposing forces in a star are
•
•

Gravity – contracts
Thermal nuclear energy – expands

 Stages
•

Birth
•

•
•
•
•

In dark, cool, interstellar clouds
Gravity contracts the cloud
Temperature rises
Radiates long-wavelength (red) light
Becomes a protostar

24.2 Stellar evolution (continued)
 Stages
•

Protostar
•
•
•

•
•
•
•

Gravitational contraction of gaseous cloud
continues
Core reaches 10 million K
Hydrogen nuclei fuse
• Become helium nuclei
• Process is called hydrogen burning
Energy is released
Outward pressure increases
Outward pressure balanced by gravity pulling in
Star becomes a stable main-sequence star

24.2 Stellar evolution (continued)
 Stages
•

Main-sequence stage
•

Stars age at different rates
• Massive stars use fuel faster and exist for
only a few million years
• Small stars use fuel slowly and exist for
perhaps hundreds of billions of years

•

90% of a star's life is in the main-sequence

24.2 Stellar evolution (continued)
 Stages
•

Red giant stage
•
•

•
•
•

Hydrogen burning migrates outward
Star's outer envelope expands
• Surface cools
• Surface becomes red
Core is collapsing as helium is converted to
carbon
Eventually all nuclear fuel is used
Gravity squeezes the star

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Low-mass star
• 0.5 solar mass
• Red giant collapses
• Becomes a white dwarf

24.2 Evolutionary stages of
low mass stars

Figure 24.12 A

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Medium-mass star
• Between 0.5 and 3 solar masses
• Red giant collapses
• Planetary nebula forms
• Becomes a white dwarf

24.2 Evolutionary stages of
medium mass stars

Figure 24.12 B

H-R diagram showing
stellar evolution

Figure 24.11

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Massive star
• Over 3 solar masses
• Short life span
• Terminates in a brilliant explosion called
a supernova
• Interior condenses
• May produce a hot, dense object that is
either a neutron star or a black hole

24.2 Evolutionary stages of
massive stars

Figure 24.12 C

24.2 Stellar remnants
 White
•
•

Small (some no larger than Earth)
Dense
•
•
•

•
•

dwarf

Can be more massive than the Sun
Spoonful weighs several tons
Atoms take up less space
• Electrons displaced inward
• Called degenerate matter

Hot surface
Cools to become a black dwarf

24.2 Stellar remnants (continued)
 Neutron
•

Forms from a more massive star
•
•

•
•

star

Star has more gravity
Squeezes itself smaller

Remnant of a supernova
Gravitational force collapses atoms
•
•

Electrons combine with protons to produce
neutrons
Small size

24.2 Stellar remnants (continued)
 Neutron
•

Pea size sample
•
•

•
•

star

Weighs 100 million tons
Same density as an atomic nucleus

Strong magnetic field
First one discovered in early 1970s
•
•

Pulsar (pulsating radio source)
Found in the Crab nebula (remnant of an A.D.
1054 supernova)

Crab Nebula in the
constellation Taurus

Figure 24.14

24.2 Stellar remnants (continued)
 Black
•
•

•

More dense than a neutron star
Intense surface gravity lets no light escape
As matter is pulled into it
•
•

•

hole

Becomes very hot
Emits x-rays

Likely candidate is Cygnus X-1, a strong xray source

Quiz Break

24.3 Galaxies
 Milky
•

Way galaxy

Structure
•
•

•
•

Determined by using radio telescopes
Large spiral galaxy
• About 100,000 light-years wide
• Thickness at the galactic nucleus is about
10,000 light-years
Three spiral arms of stars
Sun is 30,000 light-years from the center

Face-on view of the
Milk Way Galaxy

Figure 24.18 A

Edge-on view of the
Milk Way Galaxy

Figure 24.18 B

24.3 Galaxies (continued)
 Milky
•

Rotation
•
•
•

•

Way galaxy

Around the galactic nucleus
Outermost stars move the slowest
Sun rotates around the galactic nucleus once
about every 200 million years

Halo surrounds the galactic disk
•
•
•

Spherical
Very tenuous gas
Numerous globular clusters

24.3 Galaxies (continued)
 Other
•
•

galaxies

Existence was first proposed in mid-1700s
by Immanuel Kant
Four basic types of galaxies
•

Spiral galaxy
• Arms extending from nucleus
• About 30% of all galaxies
• Large diameter of 20,000 to 125,000 light
years
• Contains both young and old stars
• e.g., Milky Way

Great Galaxy, a spiral galaxy, in
the constellation Andromeda

Figure 24.20

24.3 Galaxies (continued)
 Other
•

galaxies

Four basic types of galaxies
•

•

Barred spiral galaxy
• Stars arranged in the shape of a bar
• Generally quite large
• About 10% of all galaxies
Elliptical galaxy
• Ellipsoidal shape
• About 60% of all galaxies
• Most are smaller than spiral galaxies;
however, they are also the largest known
galaxies

A barred spiral galaxy

Figure 24.22

24.3 Galaxies (continued)
 Other
•

galaxies

Four basic types of galaxies
•

Irregular galaxy
• Lacks symmetry
• About 10% of all galaxies
• Contains mostly young stars
• e.g., Magellanic Clouds

24.3 Galaxies (continued)
 Galactic
•
•
•

Group of galaxies
Some contain thousands of galaxies
Local Group
•
•

•

cluster

Our own group of galaxies
Contains at least 28 galaxies

Supercluster
•
•

Huge swarm of galaxies
May be the largest entity in the universe

Quiz Break

24.4 Red shifts
 Doppler
•

effect

Change in the wavelength of light emitted
by an object due to its motion
•

•

Movement away stretches the wavelength
• Longer wavelength
• Light appears redder
Movement toward “squeezes” the wavelength
• Shorter wavelength
• Light shifted toward the blue

24.4 Red shifts (continued)
 Doppler
•

effect

Amount of the Doppler shift indicates the
rate of movement
•
•

Large Doppler shift indicates a high velocity
Small Doppler shift indicates a lower velocity

 Expanding
•

universe

Most galaxies exhibit a red Doppler shift
•

Moving away

Raisin bread analogy of an
expanding universe

Figure 24.24

24.4 Red shifts (continued)
 Expanding
•

universe

Most galaxies exhibit a red Doppler shift
•

•
•
•

Far galaxies
• Exhibit the greatest shift
• Greater velocity
Discovered in 1929 by Edwin Hubble
Hubble's Law – the recessional speed of
galaxies is proportional to their distance
Accounts for red shifts

24.4 Big Bang theory
 Accounts

for galaxies moving away

from us
 Universe was once confined to a "ball"
that was
•
•

•

Supermassive
Dense
Hot

24.4 Big Bang theory (continued)
 Big

Bang marks the inception of the
universe
•
•

Occurred about 15 billion years ago
All matter and space was created

 Matter

is moving outward
 Fate of the universe
•

Two possibilities
•
•

Universe will last forever
Outward expansion sill stop and gravitational;
contraction will follow

24.4 Big Bang theory (continued)
 Fate
•

of the universe

Final fate depends on the average density
of the universe
•
•

If the density is more than the critical density,
then the universe would contract
Current estimates point to less then the critical
density and predict an ever-expanding, or
open, universe

Chapter 24Test Guidance
You will be responsible on the test for answering 3 of the following 6
questions.
1.

2.

3.
4.
5.
6.

What causes the difference between a star’s apparent
magnitude and it absolute magnitude.
List and explain the three factors that control the apparent
brightness of a star as seen from Earth.
Describe how binary stars are used to determine stellar mass.
List and describe the four basic types of galaxies.
What is Hubble’s Law, please explain in detail.
Briefly describe the Big Bang Theory (not the TV show).

End of Chapter 24


Slide 35

Lecture Outlines
PowerPoint

Chapter 24
Earth Science 11e
Tarbuck/Lutgens
Modified for educational
purposes only
By S. Koziol 12-8-2010

© 2006 Pearson Prentice Hall

Earth Science, 11e
Beyond Our
Solar System
Chapter 24

24.1 Properties of stars
 Distance
•
•

Measuring a star's distance can be very
difficult
Stellar parallax
•
•
•

•
•

Used for measuring distance to a star
Apparent shift in a star's position due to the
orbital motion of Earth
Measured as an angle
Near stars have the largest parallax
Largest parallax is less than one second of arc

24. 1 Properties of stars
(continued)

 Distance
•
•

Distances to the stars are very large
Units of measurement
•
•

•

Kilometers or astronomical units are too
cumbersome to use
Light-year is used most often
• Distance that light travels in 1 year
• One light-year is 9.5 trillion km (5.8 trillion
miles)

Other methods for measuring distance are
also used

24. 1 Properties of stars
(continued)

 Stellar
•

Controlled by three factors
•

•
•

•

brightness

Size
Temperature
Distance

Magnitude
•

Measure of a star's brightness

24.1 Properties of stars
(continued)

 Stellar
•

brightness

Magnitude
•

Two types of measurement
• Apparent magnitude
• Brightness when a star is viewed from
Earth
• Decreases with distance
• Numbers are used to designate
magnitudes - dim stars have large
numbers and negative numbers are also
used

24.1 Properties of stars
(continued)

 Stellar
•

brightness

Magnitude
•

Two types of measurement
• Absolute magnitude
• "True" or intrinsic brightness of a star
• Brightness at a standard distance of
32.6 light-years
• Most stars' absolute magnitudes are
between -5 and +15

24.1 Properties of stars
(continued)

 Color
•

Hot star
•

•
•

•

and temperature

Temperature above 30,000 K
Emits short-wavelength light
Appears blue

Cool star
•
•
•

Temperature less than 3000 K
Emits longer-wavelength light
Appears red

24.1 Properties of stars
(continued)

 Color
•

and temperature

Between 5000 and 6000 K
•
•

Stars appear yellow
e.g., Sun

 Binary
•

stars and stellar mass

Binary stars
•

Two stars orbiting one another
• Stars are held together by mutual
gravitation
• Both orbit around a common center of mass

24.1 Properties of stars (continued)
 Binary
•

Binary stars
•

•
•

•

stars and stellar mass

Visual binaries are resolved telescopically
More than 50% of the stars in the universe are
binary stars
Used to determine stellar mass

Stellar mass
•

Determined using binary stars – the center of
mass is closest to the most massive star

Binary stars
orbit each
other around
their common
center of
mass
Figure 24.4

24.1 Properties of stars (continued)
 Binary
•

stars and stellar mass

Stellar mass
•

Mass of most stars is between one-tenth and
fifty times the mass of the Sun

24.1 Hertzsprung-Russell
diagram
 Shows
•
•

the relation between stellar

Brightness (absolute magnitude) and
Temperature

 Diagram

is made by plotting (graphing)
each star's
•
•

Luminosity (brightness) and
Temperature

24.1 Hertzsprung-Russell
diagram (continued)
 Parts
•

Main-sequence stars
•

•
•

•

of an H-R diagram

90% of all stars
Band through the center of the H-R diagram
Sun is in the main-sequence

Giants (or red giants)
•
•
•

Very luminous
Large
Upper-right on the H-R diagram

24.1 Hertzsprung-Russell
diagram (continued)
 Parts
•

Giants (or red giants)
•

•

•

of an H-R diagram

Very large giants are called supergiants
Only a few percent of all stars

White dwarfs
•
•

•
•
•

Fainter than main-sequence stars
Small (approximate the size of Earth)
Lower-central area on the H-R diagram
Not all are white in color
Perhaps 10% of all stars

Idealized HertzsprungRussell diagram

Figure 24.5

Quiz Break

24.2 Variable stars
 Stars

that fluctuate in brightness
 Types of variable stars
•

Pulsating variables
•
•

•

Fluctuate regularly in brightness
Expand and contract in size

Eruptive variables
•
•
•

Explosive event
Sudden brightening
Called a nova

24.2 Interstellar matter
 Between

the stars is "the vacuum of

space"
 Nebula
•
•

Cloud of dust and gases
Two major types of nebulae
•

Bright nebula
• Glows if it close to a very hot star
• Two types of bright nebulae
• Emission nebula
• Reflection nebula

The Orion Nebula is a wellknown emission nebula

Figure 24.8

A faint blue reflection nebula in
the Pleiades star cluster

Figure 24.9

24.2 Interstellar matter (continued)
 Nebula
•

Two major types of nebulae
•

Dark nebula
• Not close to any bright star
• Appear dark
• Contains the material that forms stars and
planets

24.2 Stellar evolution
 Stars

exist because of gravity
 Two opposing forces in a star are
•
•

Gravity – contracts
Thermal nuclear energy – expands

 Stages
•

Birth
•

•
•
•
•

In dark, cool, interstellar clouds
Gravity contracts the cloud
Temperature rises
Radiates long-wavelength (red) light
Becomes a protostar

24.2 Stellar evolution (continued)
 Stages
•

Protostar
•
•
•

•
•
•
•

Gravitational contraction of gaseous cloud
continues
Core reaches 10 million K
Hydrogen nuclei fuse
• Become helium nuclei
• Process is called hydrogen burning
Energy is released
Outward pressure increases
Outward pressure balanced by gravity pulling in
Star becomes a stable main-sequence star

24.2 Stellar evolution (continued)
 Stages
•

Main-sequence stage
•

Stars age at different rates
• Massive stars use fuel faster and exist for
only a few million years
• Small stars use fuel slowly and exist for
perhaps hundreds of billions of years

•

90% of a star's life is in the main-sequence

24.2 Stellar evolution (continued)
 Stages
•

Red giant stage
•
•

•
•
•

Hydrogen burning migrates outward
Star's outer envelope expands
• Surface cools
• Surface becomes red
Core is collapsing as helium is converted to
carbon
Eventually all nuclear fuel is used
Gravity squeezes the star

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Low-mass star
• 0.5 solar mass
• Red giant collapses
• Becomes a white dwarf

24.2 Evolutionary stages of
low mass stars

Figure 24.12 A

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Medium-mass star
• Between 0.5 and 3 solar masses
• Red giant collapses
• Planetary nebula forms
• Becomes a white dwarf

24.2 Evolutionary stages of
medium mass stars

Figure 24.12 B

H-R diagram showing
stellar evolution

Figure 24.11

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Massive star
• Over 3 solar masses
• Short life span
• Terminates in a brilliant explosion called
a supernova
• Interior condenses
• May produce a hot, dense object that is
either a neutron star or a black hole

24.2 Evolutionary stages of
massive stars

Figure 24.12 C

24.2 Stellar remnants
 White
•
•

Small (some no larger than Earth)
Dense
•
•
•

•
•

dwarf

Can be more massive than the Sun
Spoonful weighs several tons
Atoms take up less space
• Electrons displaced inward
• Called degenerate matter

Hot surface
Cools to become a black dwarf

24.2 Stellar remnants (continued)
 Neutron
•

Forms from a more massive star
•
•

•
•

star

Star has more gravity
Squeezes itself smaller

Remnant of a supernova
Gravitational force collapses atoms
•
•

Electrons combine with protons to produce
neutrons
Small size

24.2 Stellar remnants (continued)
 Neutron
•

Pea size sample
•
•

•
•

star

Weighs 100 million tons
Same density as an atomic nucleus

Strong magnetic field
First one discovered in early 1970s
•
•

Pulsar (pulsating radio source)
Found in the Crab nebula (remnant of an A.D.
1054 supernova)

Crab Nebula in the
constellation Taurus

Figure 24.14

24.2 Stellar remnants (continued)
 Black
•
•

•

More dense than a neutron star
Intense surface gravity lets no light escape
As matter is pulled into it
•
•

•

hole

Becomes very hot
Emits x-rays

Likely candidate is Cygnus X-1, a strong xray source

Quiz Break

24.3 Galaxies
 Milky
•

Way galaxy

Structure
•
•

•
•

Determined by using radio telescopes
Large spiral galaxy
• About 100,000 light-years wide
• Thickness at the galactic nucleus is about
10,000 light-years
Three spiral arms of stars
Sun is 30,000 light-years from the center

Face-on view of the
Milk Way Galaxy

Figure 24.18 A

Edge-on view of the
Milk Way Galaxy

Figure 24.18 B

24.3 Galaxies (continued)
 Milky
•

Rotation
•
•
•

•

Way galaxy

Around the galactic nucleus
Outermost stars move the slowest
Sun rotates around the galactic nucleus once
about every 200 million years

Halo surrounds the galactic disk
•
•
•

Spherical
Very tenuous gas
Numerous globular clusters

24.3 Galaxies (continued)
 Other
•
•

galaxies

Existence was first proposed in mid-1700s
by Immanuel Kant
Four basic types of galaxies
•

Spiral galaxy
• Arms extending from nucleus
• About 30% of all galaxies
• Large diameter of 20,000 to 125,000 light
years
• Contains both young and old stars
• e.g., Milky Way

Great Galaxy, a spiral galaxy, in
the constellation Andromeda

Figure 24.20

24.3 Galaxies (continued)
 Other
•

galaxies

Four basic types of galaxies
•

•

Barred spiral galaxy
• Stars arranged in the shape of a bar
• Generally quite large
• About 10% of all galaxies
Elliptical galaxy
• Ellipsoidal shape
• About 60% of all galaxies
• Most are smaller than spiral galaxies;
however, they are also the largest known
galaxies

A barred spiral galaxy

Figure 24.22

24.3 Galaxies (continued)
 Other
•

galaxies

Four basic types of galaxies
•

Irregular galaxy
• Lacks symmetry
• About 10% of all galaxies
• Contains mostly young stars
• e.g., Magellanic Clouds

24.3 Galaxies (continued)
 Galactic
•
•
•

Group of galaxies
Some contain thousands of galaxies
Local Group
•
•

•

cluster

Our own group of galaxies
Contains at least 28 galaxies

Supercluster
•
•

Huge swarm of galaxies
May be the largest entity in the universe

Quiz Break

24.4 Red shifts
 Doppler
•

effect

Change in the wavelength of light emitted
by an object due to its motion
•

•

Movement away stretches the wavelength
• Longer wavelength
• Light appears redder
Movement toward “squeezes” the wavelength
• Shorter wavelength
• Light shifted toward the blue

24.4 Red shifts (continued)
 Doppler
•

effect

Amount of the Doppler shift indicates the
rate of movement
•
•

Large Doppler shift indicates a high velocity
Small Doppler shift indicates a lower velocity

 Expanding
•

universe

Most galaxies exhibit a red Doppler shift
•

Moving away

Raisin bread analogy of an
expanding universe

Figure 24.24

24.4 Red shifts (continued)
 Expanding
•

universe

Most galaxies exhibit a red Doppler shift
•

•
•
•

Far galaxies
• Exhibit the greatest shift
• Greater velocity
Discovered in 1929 by Edwin Hubble
Hubble's Law – the recessional speed of
galaxies is proportional to their distance
Accounts for red shifts

24.4 Big Bang theory
 Accounts

for galaxies moving away

from us
 Universe was once confined to a "ball"
that was
•
•

•

Supermassive
Dense
Hot

24.4 Big Bang theory (continued)
 Big

Bang marks the inception of the
universe
•
•

Occurred about 15 billion years ago
All matter and space was created

 Matter

is moving outward
 Fate of the universe
•

Two possibilities
•
•

Universe will last forever
Outward expansion sill stop and gravitational;
contraction will follow

24.4 Big Bang theory (continued)
 Fate
•

of the universe

Final fate depends on the average density
of the universe
•
•

If the density is more than the critical density,
then the universe would contract
Current estimates point to less then the critical
density and predict an ever-expanding, or
open, universe

Chapter 24Test Guidance
You will be responsible on the test for answering 3 of the following 6
questions.
1.

2.

3.
4.
5.
6.

What causes the difference between a star’s apparent
magnitude and it absolute magnitude.
List and explain the three factors that control the apparent
brightness of a star as seen from Earth.
Describe how binary stars are used to determine stellar mass.
List and describe the four basic types of galaxies.
What is Hubble’s Law, please explain in detail.
Briefly describe the Big Bang Theory (not the TV show).

End of Chapter 24


Slide 36

Lecture Outlines
PowerPoint

Chapter 24
Earth Science 11e
Tarbuck/Lutgens
Modified for educational
purposes only
By S. Koziol 12-8-2010

© 2006 Pearson Prentice Hall

Earth Science, 11e
Beyond Our
Solar System
Chapter 24

24.1 Properties of stars
 Distance
•
•

Measuring a star's distance can be very
difficult
Stellar parallax
•
•
•

•
•

Used for measuring distance to a star
Apparent shift in a star's position due to the
orbital motion of Earth
Measured as an angle
Near stars have the largest parallax
Largest parallax is less than one second of arc

24. 1 Properties of stars
(continued)

 Distance
•
•

Distances to the stars are very large
Units of measurement
•
•

•

Kilometers or astronomical units are too
cumbersome to use
Light-year is used most often
• Distance that light travels in 1 year
• One light-year is 9.5 trillion km (5.8 trillion
miles)

Other methods for measuring distance are
also used

24. 1 Properties of stars
(continued)

 Stellar
•

Controlled by three factors
•

•
•

•

brightness

Size
Temperature
Distance

Magnitude
•

Measure of a star's brightness

24.1 Properties of stars
(continued)

 Stellar
•

brightness

Magnitude
•

Two types of measurement
• Apparent magnitude
• Brightness when a star is viewed from
Earth
• Decreases with distance
• Numbers are used to designate
magnitudes - dim stars have large
numbers and negative numbers are also
used

24.1 Properties of stars
(continued)

 Stellar
•

brightness

Magnitude
•

Two types of measurement
• Absolute magnitude
• "True" or intrinsic brightness of a star
• Brightness at a standard distance of
32.6 light-years
• Most stars' absolute magnitudes are
between -5 and +15

24.1 Properties of stars
(continued)

 Color
•

Hot star
•

•
•

•

and temperature

Temperature above 30,000 K
Emits short-wavelength light
Appears blue

Cool star
•
•
•

Temperature less than 3000 K
Emits longer-wavelength light
Appears red

24.1 Properties of stars
(continued)

 Color
•

and temperature

Between 5000 and 6000 K
•
•

Stars appear yellow
e.g., Sun

 Binary
•

stars and stellar mass

Binary stars
•

Two stars orbiting one another
• Stars are held together by mutual
gravitation
• Both orbit around a common center of mass

24.1 Properties of stars (continued)
 Binary
•

Binary stars
•

•
•

•

stars and stellar mass

Visual binaries are resolved telescopically
More than 50% of the stars in the universe are
binary stars
Used to determine stellar mass

Stellar mass
•

Determined using binary stars – the center of
mass is closest to the most massive star

Binary stars
orbit each
other around
their common
center of
mass
Figure 24.4

24.1 Properties of stars (continued)
 Binary
•

stars and stellar mass

Stellar mass
•

Mass of most stars is between one-tenth and
fifty times the mass of the Sun

24.1 Hertzsprung-Russell
diagram
 Shows
•
•

the relation between stellar

Brightness (absolute magnitude) and
Temperature

 Diagram

is made by plotting (graphing)
each star's
•
•

Luminosity (brightness) and
Temperature

24.1 Hertzsprung-Russell
diagram (continued)
 Parts
•

Main-sequence stars
•

•
•

•

of an H-R diagram

90% of all stars
Band through the center of the H-R diagram
Sun is in the main-sequence

Giants (or red giants)
•
•
•

Very luminous
Large
Upper-right on the H-R diagram

24.1 Hertzsprung-Russell
diagram (continued)
 Parts
•

Giants (or red giants)
•

•

•

of an H-R diagram

Very large giants are called supergiants
Only a few percent of all stars

White dwarfs
•
•

•
•
•

Fainter than main-sequence stars
Small (approximate the size of Earth)
Lower-central area on the H-R diagram
Not all are white in color
Perhaps 10% of all stars

Idealized HertzsprungRussell diagram

Figure 24.5

Quiz Break

24.2 Variable stars
 Stars

that fluctuate in brightness
 Types of variable stars
•

Pulsating variables
•
•

•

Fluctuate regularly in brightness
Expand and contract in size

Eruptive variables
•
•
•

Explosive event
Sudden brightening
Called a nova

24.2 Interstellar matter
 Between

the stars is "the vacuum of

space"
 Nebula
•
•

Cloud of dust and gases
Two major types of nebulae
•

Bright nebula
• Glows if it close to a very hot star
• Two types of bright nebulae
• Emission nebula
• Reflection nebula

The Orion Nebula is a wellknown emission nebula

Figure 24.8

A faint blue reflection nebula in
the Pleiades star cluster

Figure 24.9

24.2 Interstellar matter (continued)
 Nebula
•

Two major types of nebulae
•

Dark nebula
• Not close to any bright star
• Appear dark
• Contains the material that forms stars and
planets

24.2 Stellar evolution
 Stars

exist because of gravity
 Two opposing forces in a star are
•
•

Gravity – contracts
Thermal nuclear energy – expands

 Stages
•

Birth
•

•
•
•
•

In dark, cool, interstellar clouds
Gravity contracts the cloud
Temperature rises
Radiates long-wavelength (red) light
Becomes a protostar

24.2 Stellar evolution (continued)
 Stages
•

Protostar
•
•
•

•
•
•
•

Gravitational contraction of gaseous cloud
continues
Core reaches 10 million K
Hydrogen nuclei fuse
• Become helium nuclei
• Process is called hydrogen burning
Energy is released
Outward pressure increases
Outward pressure balanced by gravity pulling in
Star becomes a stable main-sequence star

24.2 Stellar evolution (continued)
 Stages
•

Main-sequence stage
•

Stars age at different rates
• Massive stars use fuel faster and exist for
only a few million years
• Small stars use fuel slowly and exist for
perhaps hundreds of billions of years

•

90% of a star's life is in the main-sequence

24.2 Stellar evolution (continued)
 Stages
•

Red giant stage
•
•

•
•
•

Hydrogen burning migrates outward
Star's outer envelope expands
• Surface cools
• Surface becomes red
Core is collapsing as helium is converted to
carbon
Eventually all nuclear fuel is used
Gravity squeezes the star

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Low-mass star
• 0.5 solar mass
• Red giant collapses
• Becomes a white dwarf

24.2 Evolutionary stages of
low mass stars

Figure 24.12 A

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Medium-mass star
• Between 0.5 and 3 solar masses
• Red giant collapses
• Planetary nebula forms
• Becomes a white dwarf

24.2 Evolutionary stages of
medium mass stars

Figure 24.12 B

H-R diagram showing
stellar evolution

Figure 24.11

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Massive star
• Over 3 solar masses
• Short life span
• Terminates in a brilliant explosion called
a supernova
• Interior condenses
• May produce a hot, dense object that is
either a neutron star or a black hole

24.2 Evolutionary stages of
massive stars

Figure 24.12 C

24.2 Stellar remnants
 White
•
•

Small (some no larger than Earth)
Dense
•
•
•

•
•

dwarf

Can be more massive than the Sun
Spoonful weighs several tons
Atoms take up less space
• Electrons displaced inward
• Called degenerate matter

Hot surface
Cools to become a black dwarf

24.2 Stellar remnants (continued)
 Neutron
•

Forms from a more massive star
•
•

•
•

star

Star has more gravity
Squeezes itself smaller

Remnant of a supernova
Gravitational force collapses atoms
•
•

Electrons combine with protons to produce
neutrons
Small size

24.2 Stellar remnants (continued)
 Neutron
•

Pea size sample
•
•

•
•

star

Weighs 100 million tons
Same density as an atomic nucleus

Strong magnetic field
First one discovered in early 1970s
•
•

Pulsar (pulsating radio source)
Found in the Crab nebula (remnant of an A.D.
1054 supernova)

Crab Nebula in the
constellation Taurus

Figure 24.14

24.2 Stellar remnants (continued)
 Black
•
•

•

More dense than a neutron star
Intense surface gravity lets no light escape
As matter is pulled into it
•
•

•

hole

Becomes very hot
Emits x-rays

Likely candidate is Cygnus X-1, a strong xray source

Quiz Break

24.3 Galaxies
 Milky
•

Way galaxy

Structure
•
•

•
•

Determined by using radio telescopes
Large spiral galaxy
• About 100,000 light-years wide
• Thickness at the galactic nucleus is about
10,000 light-years
Three spiral arms of stars
Sun is 30,000 light-years from the center

Face-on view of the
Milk Way Galaxy

Figure 24.18 A

Edge-on view of the
Milk Way Galaxy

Figure 24.18 B

24.3 Galaxies (continued)
 Milky
•

Rotation
•
•
•

•

Way galaxy

Around the galactic nucleus
Outermost stars move the slowest
Sun rotates around the galactic nucleus once
about every 200 million years

Halo surrounds the galactic disk
•
•
•

Spherical
Very tenuous gas
Numerous globular clusters

24.3 Galaxies (continued)
 Other
•
•

galaxies

Existence was first proposed in mid-1700s
by Immanuel Kant
Four basic types of galaxies
•

Spiral galaxy
• Arms extending from nucleus
• About 30% of all galaxies
• Large diameter of 20,000 to 125,000 light
years
• Contains both young and old stars
• e.g., Milky Way

Great Galaxy, a spiral galaxy, in
the constellation Andromeda

Figure 24.20

24.3 Galaxies (continued)
 Other
•

galaxies

Four basic types of galaxies
•

•

Barred spiral galaxy
• Stars arranged in the shape of a bar
• Generally quite large
• About 10% of all galaxies
Elliptical galaxy
• Ellipsoidal shape
• About 60% of all galaxies
• Most are smaller than spiral galaxies;
however, they are also the largest known
galaxies

A barred spiral galaxy

Figure 24.22

24.3 Galaxies (continued)
 Other
•

galaxies

Four basic types of galaxies
•

Irregular galaxy
• Lacks symmetry
• About 10% of all galaxies
• Contains mostly young stars
• e.g., Magellanic Clouds

24.3 Galaxies (continued)
 Galactic
•
•
•

Group of galaxies
Some contain thousands of galaxies
Local Group
•
•

•

cluster

Our own group of galaxies
Contains at least 28 galaxies

Supercluster
•
•

Huge swarm of galaxies
May be the largest entity in the universe

Quiz Break

24.4 Red shifts
 Doppler
•

effect

Change in the wavelength of light emitted
by an object due to its motion
•

•

Movement away stretches the wavelength
• Longer wavelength
• Light appears redder
Movement toward “squeezes” the wavelength
• Shorter wavelength
• Light shifted toward the blue

24.4 Red shifts (continued)
 Doppler
•

effect

Amount of the Doppler shift indicates the
rate of movement
•
•

Large Doppler shift indicates a high velocity
Small Doppler shift indicates a lower velocity

 Expanding
•

universe

Most galaxies exhibit a red Doppler shift
•

Moving away

Raisin bread analogy of an
expanding universe

Figure 24.24

24.4 Red shifts (continued)
 Expanding
•

universe

Most galaxies exhibit a red Doppler shift
•

•
•
•

Far galaxies
• Exhibit the greatest shift
• Greater velocity
Discovered in 1929 by Edwin Hubble
Hubble's Law – the recessional speed of
galaxies is proportional to their distance
Accounts for red shifts

24.4 Big Bang theory
 Accounts

for galaxies moving away

from us
 Universe was once confined to a "ball"
that was
•
•

•

Supermassive
Dense
Hot

24.4 Big Bang theory (continued)
 Big

Bang marks the inception of the
universe
•
•

Occurred about 15 billion years ago
All matter and space was created

 Matter

is moving outward
 Fate of the universe
•

Two possibilities
•
•

Universe will last forever
Outward expansion sill stop and gravitational;
contraction will follow

24.4 Big Bang theory (continued)
 Fate
•

of the universe

Final fate depends on the average density
of the universe
•
•

If the density is more than the critical density,
then the universe would contract
Current estimates point to less then the critical
density and predict an ever-expanding, or
open, universe

Chapter 24Test Guidance
You will be responsible on the test for answering 3 of the following 6
questions.
1.

2.

3.
4.
5.
6.

What causes the difference between a star’s apparent
magnitude and it absolute magnitude.
List and explain the three factors that control the apparent
brightness of a star as seen from Earth.
Describe how binary stars are used to determine stellar mass.
List and describe the four basic types of galaxies.
What is Hubble’s Law, please explain in detail.
Briefly describe the Big Bang Theory (not the TV show).

End of Chapter 24


Slide 37

Lecture Outlines
PowerPoint

Chapter 24
Earth Science 11e
Tarbuck/Lutgens
Modified for educational
purposes only
By S. Koziol 12-8-2010

© 2006 Pearson Prentice Hall

Earth Science, 11e
Beyond Our
Solar System
Chapter 24

24.1 Properties of stars
 Distance
•
•

Measuring a star's distance can be very
difficult
Stellar parallax
•
•
•

•
•

Used for measuring distance to a star
Apparent shift in a star's position due to the
orbital motion of Earth
Measured as an angle
Near stars have the largest parallax
Largest parallax is less than one second of arc

24. 1 Properties of stars
(continued)

 Distance
•
•

Distances to the stars are very large
Units of measurement
•
•

•

Kilometers or astronomical units are too
cumbersome to use
Light-year is used most often
• Distance that light travels in 1 year
• One light-year is 9.5 trillion km (5.8 trillion
miles)

Other methods for measuring distance are
also used

24. 1 Properties of stars
(continued)

 Stellar
•

Controlled by three factors
•

•
•

•

brightness

Size
Temperature
Distance

Magnitude
•

Measure of a star's brightness

24.1 Properties of stars
(continued)

 Stellar
•

brightness

Magnitude
•

Two types of measurement
• Apparent magnitude
• Brightness when a star is viewed from
Earth
• Decreases with distance
• Numbers are used to designate
magnitudes - dim stars have large
numbers and negative numbers are also
used

24.1 Properties of stars
(continued)

 Stellar
•

brightness

Magnitude
•

Two types of measurement
• Absolute magnitude
• "True" or intrinsic brightness of a star
• Brightness at a standard distance of
32.6 light-years
• Most stars' absolute magnitudes are
between -5 and +15

24.1 Properties of stars
(continued)

 Color
•

Hot star
•

•
•

•

and temperature

Temperature above 30,000 K
Emits short-wavelength light
Appears blue

Cool star
•
•
•

Temperature less than 3000 K
Emits longer-wavelength light
Appears red

24.1 Properties of stars
(continued)

 Color
•

and temperature

Between 5000 and 6000 K
•
•

Stars appear yellow
e.g., Sun

 Binary
•

stars and stellar mass

Binary stars
•

Two stars orbiting one another
• Stars are held together by mutual
gravitation
• Both orbit around a common center of mass

24.1 Properties of stars (continued)
 Binary
•

Binary stars
•

•
•

•

stars and stellar mass

Visual binaries are resolved telescopically
More than 50% of the stars in the universe are
binary stars
Used to determine stellar mass

Stellar mass
•

Determined using binary stars – the center of
mass is closest to the most massive star

Binary stars
orbit each
other around
their common
center of
mass
Figure 24.4

24.1 Properties of stars (continued)
 Binary
•

stars and stellar mass

Stellar mass
•

Mass of most stars is between one-tenth and
fifty times the mass of the Sun

24.1 Hertzsprung-Russell
diagram
 Shows
•
•

the relation between stellar

Brightness (absolute magnitude) and
Temperature

 Diagram

is made by plotting (graphing)
each star's
•
•

Luminosity (brightness) and
Temperature

24.1 Hertzsprung-Russell
diagram (continued)
 Parts
•

Main-sequence stars
•

•
•

•

of an H-R diagram

90% of all stars
Band through the center of the H-R diagram
Sun is in the main-sequence

Giants (or red giants)
•
•
•

Very luminous
Large
Upper-right on the H-R diagram

24.1 Hertzsprung-Russell
diagram (continued)
 Parts
•

Giants (or red giants)
•

•

•

of an H-R diagram

Very large giants are called supergiants
Only a few percent of all stars

White dwarfs
•
•

•
•
•

Fainter than main-sequence stars
Small (approximate the size of Earth)
Lower-central area on the H-R diagram
Not all are white in color
Perhaps 10% of all stars

Idealized HertzsprungRussell diagram

Figure 24.5

Quiz Break

24.2 Variable stars
 Stars

that fluctuate in brightness
 Types of variable stars
•

Pulsating variables
•
•

•

Fluctuate regularly in brightness
Expand and contract in size

Eruptive variables
•
•
•

Explosive event
Sudden brightening
Called a nova

24.2 Interstellar matter
 Between

the stars is "the vacuum of

space"
 Nebula
•
•

Cloud of dust and gases
Two major types of nebulae
•

Bright nebula
• Glows if it close to a very hot star
• Two types of bright nebulae
• Emission nebula
• Reflection nebula

The Orion Nebula is a wellknown emission nebula

Figure 24.8

A faint blue reflection nebula in
the Pleiades star cluster

Figure 24.9

24.2 Interstellar matter (continued)
 Nebula
•

Two major types of nebulae
•

Dark nebula
• Not close to any bright star
• Appear dark
• Contains the material that forms stars and
planets

24.2 Stellar evolution
 Stars

exist because of gravity
 Two opposing forces in a star are
•
•

Gravity – contracts
Thermal nuclear energy – expands

 Stages
•

Birth
•

•
•
•
•

In dark, cool, interstellar clouds
Gravity contracts the cloud
Temperature rises
Radiates long-wavelength (red) light
Becomes a protostar

24.2 Stellar evolution (continued)
 Stages
•

Protostar
•
•
•

•
•
•
•

Gravitational contraction of gaseous cloud
continues
Core reaches 10 million K
Hydrogen nuclei fuse
• Become helium nuclei
• Process is called hydrogen burning
Energy is released
Outward pressure increases
Outward pressure balanced by gravity pulling in
Star becomes a stable main-sequence star

24.2 Stellar evolution (continued)
 Stages
•

Main-sequence stage
•

Stars age at different rates
• Massive stars use fuel faster and exist for
only a few million years
• Small stars use fuel slowly and exist for
perhaps hundreds of billions of years

•

90% of a star's life is in the main-sequence

24.2 Stellar evolution (continued)
 Stages
•

Red giant stage
•
•

•
•
•

Hydrogen burning migrates outward
Star's outer envelope expands
• Surface cools
• Surface becomes red
Core is collapsing as helium is converted to
carbon
Eventually all nuclear fuel is used
Gravity squeezes the star

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Low-mass star
• 0.5 solar mass
• Red giant collapses
• Becomes a white dwarf

24.2 Evolutionary stages of
low mass stars

Figure 24.12 A

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Medium-mass star
• Between 0.5 and 3 solar masses
• Red giant collapses
• Planetary nebula forms
• Becomes a white dwarf

24.2 Evolutionary stages of
medium mass stars

Figure 24.12 B

H-R diagram showing
stellar evolution

Figure 24.11

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Massive star
• Over 3 solar masses
• Short life span
• Terminates in a brilliant explosion called
a supernova
• Interior condenses
• May produce a hot, dense object that is
either a neutron star or a black hole

24.2 Evolutionary stages of
massive stars

Figure 24.12 C

24.2 Stellar remnants
 White
•
•

Small (some no larger than Earth)
Dense
•
•
•

•
•

dwarf

Can be more massive than the Sun
Spoonful weighs several tons
Atoms take up less space
• Electrons displaced inward
• Called degenerate matter

Hot surface
Cools to become a black dwarf

24.2 Stellar remnants (continued)
 Neutron
•

Forms from a more massive star
•
•

•
•

star

Star has more gravity
Squeezes itself smaller

Remnant of a supernova
Gravitational force collapses atoms
•
•

Electrons combine with protons to produce
neutrons
Small size

24.2 Stellar remnants (continued)
 Neutron
•

Pea size sample
•
•

•
•

star

Weighs 100 million tons
Same density as an atomic nucleus

Strong magnetic field
First one discovered in early 1970s
•
•

Pulsar (pulsating radio source)
Found in the Crab nebula (remnant of an A.D.
1054 supernova)

Crab Nebula in the
constellation Taurus

Figure 24.14

24.2 Stellar remnants (continued)
 Black
•
•

•

More dense than a neutron star
Intense surface gravity lets no light escape
As matter is pulled into it
•
•

•

hole

Becomes very hot
Emits x-rays

Likely candidate is Cygnus X-1, a strong xray source

Quiz Break

24.3 Galaxies
 Milky
•

Way galaxy

Structure
•
•

•
•

Determined by using radio telescopes
Large spiral galaxy
• About 100,000 light-years wide
• Thickness at the galactic nucleus is about
10,000 light-years
Three spiral arms of stars
Sun is 30,000 light-years from the center

Face-on view of the
Milk Way Galaxy

Figure 24.18 A

Edge-on view of the
Milk Way Galaxy

Figure 24.18 B

24.3 Galaxies (continued)
 Milky
•

Rotation
•
•
•

•

Way galaxy

Around the galactic nucleus
Outermost stars move the slowest
Sun rotates around the galactic nucleus once
about every 200 million years

Halo surrounds the galactic disk
•
•
•

Spherical
Very tenuous gas
Numerous globular clusters

24.3 Galaxies (continued)
 Other
•
•

galaxies

Existence was first proposed in mid-1700s
by Immanuel Kant
Four basic types of galaxies
•

Spiral galaxy
• Arms extending from nucleus
• About 30% of all galaxies
• Large diameter of 20,000 to 125,000 light
years
• Contains both young and old stars
• e.g., Milky Way

Great Galaxy, a spiral galaxy, in
the constellation Andromeda

Figure 24.20

24.3 Galaxies (continued)
 Other
•

galaxies

Four basic types of galaxies
•

•

Barred spiral galaxy
• Stars arranged in the shape of a bar
• Generally quite large
• About 10% of all galaxies
Elliptical galaxy
• Ellipsoidal shape
• About 60% of all galaxies
• Most are smaller than spiral galaxies;
however, they are also the largest known
galaxies

A barred spiral galaxy

Figure 24.22

24.3 Galaxies (continued)
 Other
•

galaxies

Four basic types of galaxies
•

Irregular galaxy
• Lacks symmetry
• About 10% of all galaxies
• Contains mostly young stars
• e.g., Magellanic Clouds

24.3 Galaxies (continued)
 Galactic
•
•
•

Group of galaxies
Some contain thousands of galaxies
Local Group
•
•

•

cluster

Our own group of galaxies
Contains at least 28 galaxies

Supercluster
•
•

Huge swarm of galaxies
May be the largest entity in the universe

Quiz Break

24.4 Red shifts
 Doppler
•

effect

Change in the wavelength of light emitted
by an object due to its motion
•

•

Movement away stretches the wavelength
• Longer wavelength
• Light appears redder
Movement toward “squeezes” the wavelength
• Shorter wavelength
• Light shifted toward the blue

24.4 Red shifts (continued)
 Doppler
•

effect

Amount of the Doppler shift indicates the
rate of movement
•
•

Large Doppler shift indicates a high velocity
Small Doppler shift indicates a lower velocity

 Expanding
•

universe

Most galaxies exhibit a red Doppler shift
•

Moving away

Raisin bread analogy of an
expanding universe

Figure 24.24

24.4 Red shifts (continued)
 Expanding
•

universe

Most galaxies exhibit a red Doppler shift
•

•
•
•

Far galaxies
• Exhibit the greatest shift
• Greater velocity
Discovered in 1929 by Edwin Hubble
Hubble's Law – the recessional speed of
galaxies is proportional to their distance
Accounts for red shifts

24.4 Big Bang theory
 Accounts

for galaxies moving away

from us
 Universe was once confined to a "ball"
that was
•
•

•

Supermassive
Dense
Hot

24.4 Big Bang theory (continued)
 Big

Bang marks the inception of the
universe
•
•

Occurred about 15 billion years ago
All matter and space was created

 Matter

is moving outward
 Fate of the universe
•

Two possibilities
•
•

Universe will last forever
Outward expansion sill stop and gravitational;
contraction will follow

24.4 Big Bang theory (continued)
 Fate
•

of the universe

Final fate depends on the average density
of the universe
•
•

If the density is more than the critical density,
then the universe would contract
Current estimates point to less then the critical
density and predict an ever-expanding, or
open, universe

Chapter 24Test Guidance
You will be responsible on the test for answering 3 of the following 6
questions.
1.

2.

3.
4.
5.
6.

What causes the difference between a star’s apparent
magnitude and it absolute magnitude.
List and explain the three factors that control the apparent
brightness of a star as seen from Earth.
Describe how binary stars are used to determine stellar mass.
List and describe the four basic types of galaxies.
What is Hubble’s Law, please explain in detail.
Briefly describe the Big Bang Theory (not the TV show).

End of Chapter 24


Slide 38

Lecture Outlines
PowerPoint

Chapter 24
Earth Science 11e
Tarbuck/Lutgens
Modified for educational
purposes only
By S. Koziol 12-8-2010

© 2006 Pearson Prentice Hall

Earth Science, 11e
Beyond Our
Solar System
Chapter 24

24.1 Properties of stars
 Distance
•
•

Measuring a star's distance can be very
difficult
Stellar parallax
•
•
•

•
•

Used for measuring distance to a star
Apparent shift in a star's position due to the
orbital motion of Earth
Measured as an angle
Near stars have the largest parallax
Largest parallax is less than one second of arc

24. 1 Properties of stars
(continued)

 Distance
•
•

Distances to the stars are very large
Units of measurement
•
•

•

Kilometers or astronomical units are too
cumbersome to use
Light-year is used most often
• Distance that light travels in 1 year
• One light-year is 9.5 trillion km (5.8 trillion
miles)

Other methods for measuring distance are
also used

24. 1 Properties of stars
(continued)

 Stellar
•

Controlled by three factors
•

•
•

•

brightness

Size
Temperature
Distance

Magnitude
•

Measure of a star's brightness

24.1 Properties of stars
(continued)

 Stellar
•

brightness

Magnitude
•

Two types of measurement
• Apparent magnitude
• Brightness when a star is viewed from
Earth
• Decreases with distance
• Numbers are used to designate
magnitudes - dim stars have large
numbers and negative numbers are also
used

24.1 Properties of stars
(continued)

 Stellar
•

brightness

Magnitude
•

Two types of measurement
• Absolute magnitude
• "True" or intrinsic brightness of a star
• Brightness at a standard distance of
32.6 light-years
• Most stars' absolute magnitudes are
between -5 and +15

24.1 Properties of stars
(continued)

 Color
•

Hot star
•

•
•

•

and temperature

Temperature above 30,000 K
Emits short-wavelength light
Appears blue

Cool star
•
•
•

Temperature less than 3000 K
Emits longer-wavelength light
Appears red

24.1 Properties of stars
(continued)

 Color
•

and temperature

Between 5000 and 6000 K
•
•

Stars appear yellow
e.g., Sun

 Binary
•

stars and stellar mass

Binary stars
•

Two stars orbiting one another
• Stars are held together by mutual
gravitation
• Both orbit around a common center of mass

24.1 Properties of stars (continued)
 Binary
•

Binary stars
•

•
•

•

stars and stellar mass

Visual binaries are resolved telescopically
More than 50% of the stars in the universe are
binary stars
Used to determine stellar mass

Stellar mass
•

Determined using binary stars – the center of
mass is closest to the most massive star

Binary stars
orbit each
other around
their common
center of
mass
Figure 24.4

24.1 Properties of stars (continued)
 Binary
•

stars and stellar mass

Stellar mass
•

Mass of most stars is between one-tenth and
fifty times the mass of the Sun

24.1 Hertzsprung-Russell
diagram
 Shows
•
•

the relation between stellar

Brightness (absolute magnitude) and
Temperature

 Diagram

is made by plotting (graphing)
each star's
•
•

Luminosity (brightness) and
Temperature

24.1 Hertzsprung-Russell
diagram (continued)
 Parts
•

Main-sequence stars
•

•
•

•

of an H-R diagram

90% of all stars
Band through the center of the H-R diagram
Sun is in the main-sequence

Giants (or red giants)
•
•
•

Very luminous
Large
Upper-right on the H-R diagram

24.1 Hertzsprung-Russell
diagram (continued)
 Parts
•

Giants (or red giants)
•

•

•

of an H-R diagram

Very large giants are called supergiants
Only a few percent of all stars

White dwarfs
•
•

•
•
•

Fainter than main-sequence stars
Small (approximate the size of Earth)
Lower-central area on the H-R diagram
Not all are white in color
Perhaps 10% of all stars

Idealized HertzsprungRussell diagram

Figure 24.5

Quiz Break

24.2 Variable stars
 Stars

that fluctuate in brightness
 Types of variable stars
•

Pulsating variables
•
•

•

Fluctuate regularly in brightness
Expand and contract in size

Eruptive variables
•
•
•

Explosive event
Sudden brightening
Called a nova

24.2 Interstellar matter
 Between

the stars is "the vacuum of

space"
 Nebula
•
•

Cloud of dust and gases
Two major types of nebulae
•

Bright nebula
• Glows if it close to a very hot star
• Two types of bright nebulae
• Emission nebula
• Reflection nebula

The Orion Nebula is a wellknown emission nebula

Figure 24.8

A faint blue reflection nebula in
the Pleiades star cluster

Figure 24.9

24.2 Interstellar matter (continued)
 Nebula
•

Two major types of nebulae
•

Dark nebula
• Not close to any bright star
• Appear dark
• Contains the material that forms stars and
planets

24.2 Stellar evolution
 Stars

exist because of gravity
 Two opposing forces in a star are
•
•

Gravity – contracts
Thermal nuclear energy – expands

 Stages
•

Birth
•

•
•
•
•

In dark, cool, interstellar clouds
Gravity contracts the cloud
Temperature rises
Radiates long-wavelength (red) light
Becomes a protostar

24.2 Stellar evolution (continued)
 Stages
•

Protostar
•
•
•

•
•
•
•

Gravitational contraction of gaseous cloud
continues
Core reaches 10 million K
Hydrogen nuclei fuse
• Become helium nuclei
• Process is called hydrogen burning
Energy is released
Outward pressure increases
Outward pressure balanced by gravity pulling in
Star becomes a stable main-sequence star

24.2 Stellar evolution (continued)
 Stages
•

Main-sequence stage
•

Stars age at different rates
• Massive stars use fuel faster and exist for
only a few million years
• Small stars use fuel slowly and exist for
perhaps hundreds of billions of years

•

90% of a star's life is in the main-sequence

24.2 Stellar evolution (continued)
 Stages
•

Red giant stage
•
•

•
•
•

Hydrogen burning migrates outward
Star's outer envelope expands
• Surface cools
• Surface becomes red
Core is collapsing as helium is converted to
carbon
Eventually all nuclear fuel is used
Gravity squeezes the star

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Low-mass star
• 0.5 solar mass
• Red giant collapses
• Becomes a white dwarf

24.2 Evolutionary stages of
low mass stars

Figure 24.12 A

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Medium-mass star
• Between 0.5 and 3 solar masses
• Red giant collapses
• Planetary nebula forms
• Becomes a white dwarf

24.2 Evolutionary stages of
medium mass stars

Figure 24.12 B

H-R diagram showing
stellar evolution

Figure 24.11

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Massive star
• Over 3 solar masses
• Short life span
• Terminates in a brilliant explosion called
a supernova
• Interior condenses
• May produce a hot, dense object that is
either a neutron star or a black hole

24.2 Evolutionary stages of
massive stars

Figure 24.12 C

24.2 Stellar remnants
 White
•
•

Small (some no larger than Earth)
Dense
•
•
•

•
•

dwarf

Can be more massive than the Sun
Spoonful weighs several tons
Atoms take up less space
• Electrons displaced inward
• Called degenerate matter

Hot surface
Cools to become a black dwarf

24.2 Stellar remnants (continued)
 Neutron
•

Forms from a more massive star
•
•

•
•

star

Star has more gravity
Squeezes itself smaller

Remnant of a supernova
Gravitational force collapses atoms
•
•

Electrons combine with protons to produce
neutrons
Small size

24.2 Stellar remnants (continued)
 Neutron
•

Pea size sample
•
•

•
•

star

Weighs 100 million tons
Same density as an atomic nucleus

Strong magnetic field
First one discovered in early 1970s
•
•

Pulsar (pulsating radio source)
Found in the Crab nebula (remnant of an A.D.
1054 supernova)

Crab Nebula in the
constellation Taurus

Figure 24.14

24.2 Stellar remnants (continued)
 Black
•
•

•

More dense than a neutron star
Intense surface gravity lets no light escape
As matter is pulled into it
•
•

•

hole

Becomes very hot
Emits x-rays

Likely candidate is Cygnus X-1, a strong xray source

Quiz Break

24.3 Galaxies
 Milky
•

Way galaxy

Structure
•
•

•
•

Determined by using radio telescopes
Large spiral galaxy
• About 100,000 light-years wide
• Thickness at the galactic nucleus is about
10,000 light-years
Three spiral arms of stars
Sun is 30,000 light-years from the center

Face-on view of the
Milk Way Galaxy

Figure 24.18 A

Edge-on view of the
Milk Way Galaxy

Figure 24.18 B

24.3 Galaxies (continued)
 Milky
•

Rotation
•
•
•

•

Way galaxy

Around the galactic nucleus
Outermost stars move the slowest
Sun rotates around the galactic nucleus once
about every 200 million years

Halo surrounds the galactic disk
•
•
•

Spherical
Very tenuous gas
Numerous globular clusters

24.3 Galaxies (continued)
 Other
•
•

galaxies

Existence was first proposed in mid-1700s
by Immanuel Kant
Four basic types of galaxies
•

Spiral galaxy
• Arms extending from nucleus
• About 30% of all galaxies
• Large diameter of 20,000 to 125,000 light
years
• Contains both young and old stars
• e.g., Milky Way

Great Galaxy, a spiral galaxy, in
the constellation Andromeda

Figure 24.20

24.3 Galaxies (continued)
 Other
•

galaxies

Four basic types of galaxies
•

•

Barred spiral galaxy
• Stars arranged in the shape of a bar
• Generally quite large
• About 10% of all galaxies
Elliptical galaxy
• Ellipsoidal shape
• About 60% of all galaxies
• Most are smaller than spiral galaxies;
however, they are also the largest known
galaxies

A barred spiral galaxy

Figure 24.22

24.3 Galaxies (continued)
 Other
•

galaxies

Four basic types of galaxies
•

Irregular galaxy
• Lacks symmetry
• About 10% of all galaxies
• Contains mostly young stars
• e.g., Magellanic Clouds

24.3 Galaxies (continued)
 Galactic
•
•
•

Group of galaxies
Some contain thousands of galaxies
Local Group
•
•

•

cluster

Our own group of galaxies
Contains at least 28 galaxies

Supercluster
•
•

Huge swarm of galaxies
May be the largest entity in the universe

Quiz Break

24.4 Red shifts
 Doppler
•

effect

Change in the wavelength of light emitted
by an object due to its motion
•

•

Movement away stretches the wavelength
• Longer wavelength
• Light appears redder
Movement toward “squeezes” the wavelength
• Shorter wavelength
• Light shifted toward the blue

24.4 Red shifts (continued)
 Doppler
•

effect

Amount of the Doppler shift indicates the
rate of movement
•
•

Large Doppler shift indicates a high velocity
Small Doppler shift indicates a lower velocity

 Expanding
•

universe

Most galaxies exhibit a red Doppler shift
•

Moving away

Raisin bread analogy of an
expanding universe

Figure 24.24

24.4 Red shifts (continued)
 Expanding
•

universe

Most galaxies exhibit a red Doppler shift
•

•
•
•

Far galaxies
• Exhibit the greatest shift
• Greater velocity
Discovered in 1929 by Edwin Hubble
Hubble's Law – the recessional speed of
galaxies is proportional to their distance
Accounts for red shifts

24.4 Big Bang theory
 Accounts

for galaxies moving away

from us
 Universe was once confined to a "ball"
that was
•
•

•

Supermassive
Dense
Hot

24.4 Big Bang theory (continued)
 Big

Bang marks the inception of the
universe
•
•

Occurred about 15 billion years ago
All matter and space was created

 Matter

is moving outward
 Fate of the universe
•

Two possibilities
•
•

Universe will last forever
Outward expansion sill stop and gravitational;
contraction will follow

24.4 Big Bang theory (continued)
 Fate
•

of the universe

Final fate depends on the average density
of the universe
•
•

If the density is more than the critical density,
then the universe would contract
Current estimates point to less then the critical
density and predict an ever-expanding, or
open, universe

Chapter 24Test Guidance
You will be responsible on the test for answering 3 of the following 6
questions.
1.

2.

3.
4.
5.
6.

What causes the difference between a star’s apparent
magnitude and it absolute magnitude.
List and explain the three factors that control the apparent
brightness of a star as seen from Earth.
Describe how binary stars are used to determine stellar mass.
List and describe the four basic types of galaxies.
What is Hubble’s Law, please explain in detail.
Briefly describe the Big Bang Theory (not the TV show).

End of Chapter 24


Slide 39

Lecture Outlines
PowerPoint

Chapter 24
Earth Science 11e
Tarbuck/Lutgens
Modified for educational
purposes only
By S. Koziol 12-8-2010

© 2006 Pearson Prentice Hall

Earth Science, 11e
Beyond Our
Solar System
Chapter 24

24.1 Properties of stars
 Distance
•
•

Measuring a star's distance can be very
difficult
Stellar parallax
•
•
•

•
•

Used for measuring distance to a star
Apparent shift in a star's position due to the
orbital motion of Earth
Measured as an angle
Near stars have the largest parallax
Largest parallax is less than one second of arc

24. 1 Properties of stars
(continued)

 Distance
•
•

Distances to the stars are very large
Units of measurement
•
•

•

Kilometers or astronomical units are too
cumbersome to use
Light-year is used most often
• Distance that light travels in 1 year
• One light-year is 9.5 trillion km (5.8 trillion
miles)

Other methods for measuring distance are
also used

24. 1 Properties of stars
(continued)

 Stellar
•

Controlled by three factors
•

•
•

•

brightness

Size
Temperature
Distance

Magnitude
•

Measure of a star's brightness

24.1 Properties of stars
(continued)

 Stellar
•

brightness

Magnitude
•

Two types of measurement
• Apparent magnitude
• Brightness when a star is viewed from
Earth
• Decreases with distance
• Numbers are used to designate
magnitudes - dim stars have large
numbers and negative numbers are also
used

24.1 Properties of stars
(continued)

 Stellar
•

brightness

Magnitude
•

Two types of measurement
• Absolute magnitude
• "True" or intrinsic brightness of a star
• Brightness at a standard distance of
32.6 light-years
• Most stars' absolute magnitudes are
between -5 and +15

24.1 Properties of stars
(continued)

 Color
•

Hot star
•

•
•

•

and temperature

Temperature above 30,000 K
Emits short-wavelength light
Appears blue

Cool star
•
•
•

Temperature less than 3000 K
Emits longer-wavelength light
Appears red

24.1 Properties of stars
(continued)

 Color
•

and temperature

Between 5000 and 6000 K
•
•

Stars appear yellow
e.g., Sun

 Binary
•

stars and stellar mass

Binary stars
•

Two stars orbiting one another
• Stars are held together by mutual
gravitation
• Both orbit around a common center of mass

24.1 Properties of stars (continued)
 Binary
•

Binary stars
•

•
•

•

stars and stellar mass

Visual binaries are resolved telescopically
More than 50% of the stars in the universe are
binary stars
Used to determine stellar mass

Stellar mass
•

Determined using binary stars – the center of
mass is closest to the most massive star

Binary stars
orbit each
other around
their common
center of
mass
Figure 24.4

24.1 Properties of stars (continued)
 Binary
•

stars and stellar mass

Stellar mass
•

Mass of most stars is between one-tenth and
fifty times the mass of the Sun

24.1 Hertzsprung-Russell
diagram
 Shows
•
•

the relation between stellar

Brightness (absolute magnitude) and
Temperature

 Diagram

is made by plotting (graphing)
each star's
•
•

Luminosity (brightness) and
Temperature

24.1 Hertzsprung-Russell
diagram (continued)
 Parts
•

Main-sequence stars
•

•
•

•

of an H-R diagram

90% of all stars
Band through the center of the H-R diagram
Sun is in the main-sequence

Giants (or red giants)
•
•
•

Very luminous
Large
Upper-right on the H-R diagram

24.1 Hertzsprung-Russell
diagram (continued)
 Parts
•

Giants (or red giants)
•

•

•

of an H-R diagram

Very large giants are called supergiants
Only a few percent of all stars

White dwarfs
•
•

•
•
•

Fainter than main-sequence stars
Small (approximate the size of Earth)
Lower-central area on the H-R diagram
Not all are white in color
Perhaps 10% of all stars

Idealized HertzsprungRussell diagram

Figure 24.5

Quiz Break

24.2 Variable stars
 Stars

that fluctuate in brightness
 Types of variable stars
•

Pulsating variables
•
•

•

Fluctuate regularly in brightness
Expand and contract in size

Eruptive variables
•
•
•

Explosive event
Sudden brightening
Called a nova

24.2 Interstellar matter
 Between

the stars is "the vacuum of

space"
 Nebula
•
•

Cloud of dust and gases
Two major types of nebulae
•

Bright nebula
• Glows if it close to a very hot star
• Two types of bright nebulae
• Emission nebula
• Reflection nebula

The Orion Nebula is a wellknown emission nebula

Figure 24.8

A faint blue reflection nebula in
the Pleiades star cluster

Figure 24.9

24.2 Interstellar matter (continued)
 Nebula
•

Two major types of nebulae
•

Dark nebula
• Not close to any bright star
• Appear dark
• Contains the material that forms stars and
planets

24.2 Stellar evolution
 Stars

exist because of gravity
 Two opposing forces in a star are
•
•

Gravity – contracts
Thermal nuclear energy – expands

 Stages
•

Birth
•

•
•
•
•

In dark, cool, interstellar clouds
Gravity contracts the cloud
Temperature rises
Radiates long-wavelength (red) light
Becomes a protostar

24.2 Stellar evolution (continued)
 Stages
•

Protostar
•
•
•

•
•
•
•

Gravitational contraction of gaseous cloud
continues
Core reaches 10 million K
Hydrogen nuclei fuse
• Become helium nuclei
• Process is called hydrogen burning
Energy is released
Outward pressure increases
Outward pressure balanced by gravity pulling in
Star becomes a stable main-sequence star

24.2 Stellar evolution (continued)
 Stages
•

Main-sequence stage
•

Stars age at different rates
• Massive stars use fuel faster and exist for
only a few million years
• Small stars use fuel slowly and exist for
perhaps hundreds of billions of years

•

90% of a star's life is in the main-sequence

24.2 Stellar evolution (continued)
 Stages
•

Red giant stage
•
•

•
•
•

Hydrogen burning migrates outward
Star's outer envelope expands
• Surface cools
• Surface becomes red
Core is collapsing as helium is converted to
carbon
Eventually all nuclear fuel is used
Gravity squeezes the star

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Low-mass star
• 0.5 solar mass
• Red giant collapses
• Becomes a white dwarf

24.2 Evolutionary stages of
low mass stars

Figure 24.12 A

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Medium-mass star
• Between 0.5 and 3 solar masses
• Red giant collapses
• Planetary nebula forms
• Becomes a white dwarf

24.2 Evolutionary stages of
medium mass stars

Figure 24.12 B

H-R diagram showing
stellar evolution

Figure 24.11

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Massive star
• Over 3 solar masses
• Short life span
• Terminates in a brilliant explosion called
a supernova
• Interior condenses
• May produce a hot, dense object that is
either a neutron star or a black hole

24.2 Evolutionary stages of
massive stars

Figure 24.12 C

24.2 Stellar remnants
 White
•
•

Small (some no larger than Earth)
Dense
•
•
•

•
•

dwarf

Can be more massive than the Sun
Spoonful weighs several tons
Atoms take up less space
• Electrons displaced inward
• Called degenerate matter

Hot surface
Cools to become a black dwarf

24.2 Stellar remnants (continued)
 Neutron
•

Forms from a more massive star
•
•

•
•

star

Star has more gravity
Squeezes itself smaller

Remnant of a supernova
Gravitational force collapses atoms
•
•

Electrons combine with protons to produce
neutrons
Small size

24.2 Stellar remnants (continued)
 Neutron
•

Pea size sample
•
•

•
•

star

Weighs 100 million tons
Same density as an atomic nucleus

Strong magnetic field
First one discovered in early 1970s
•
•

Pulsar (pulsating radio source)
Found in the Crab nebula (remnant of an A.D.
1054 supernova)

Crab Nebula in the
constellation Taurus

Figure 24.14

24.2 Stellar remnants (continued)
 Black
•
•

•

More dense than a neutron star
Intense surface gravity lets no light escape
As matter is pulled into it
•
•

•

hole

Becomes very hot
Emits x-rays

Likely candidate is Cygnus X-1, a strong xray source

Quiz Break

24.3 Galaxies
 Milky
•

Way galaxy

Structure
•
•

•
•

Determined by using radio telescopes
Large spiral galaxy
• About 100,000 light-years wide
• Thickness at the galactic nucleus is about
10,000 light-years
Three spiral arms of stars
Sun is 30,000 light-years from the center

Face-on view of the
Milk Way Galaxy

Figure 24.18 A

Edge-on view of the
Milk Way Galaxy

Figure 24.18 B

24.3 Galaxies (continued)
 Milky
•

Rotation
•
•
•

•

Way galaxy

Around the galactic nucleus
Outermost stars move the slowest
Sun rotates around the galactic nucleus once
about every 200 million years

Halo surrounds the galactic disk
•
•
•

Spherical
Very tenuous gas
Numerous globular clusters

24.3 Galaxies (continued)
 Other
•
•

galaxies

Existence was first proposed in mid-1700s
by Immanuel Kant
Four basic types of galaxies
•

Spiral galaxy
• Arms extending from nucleus
• About 30% of all galaxies
• Large diameter of 20,000 to 125,000 light
years
• Contains both young and old stars
• e.g., Milky Way

Great Galaxy, a spiral galaxy, in
the constellation Andromeda

Figure 24.20

24.3 Galaxies (continued)
 Other
•

galaxies

Four basic types of galaxies
•

•

Barred spiral galaxy
• Stars arranged in the shape of a bar
• Generally quite large
• About 10% of all galaxies
Elliptical galaxy
• Ellipsoidal shape
• About 60% of all galaxies
• Most are smaller than spiral galaxies;
however, they are also the largest known
galaxies

A barred spiral galaxy

Figure 24.22

24.3 Galaxies (continued)
 Other
•

galaxies

Four basic types of galaxies
•

Irregular galaxy
• Lacks symmetry
• About 10% of all galaxies
• Contains mostly young stars
• e.g., Magellanic Clouds

24.3 Galaxies (continued)
 Galactic
•
•
•

Group of galaxies
Some contain thousands of galaxies
Local Group
•
•

•

cluster

Our own group of galaxies
Contains at least 28 galaxies

Supercluster
•
•

Huge swarm of galaxies
May be the largest entity in the universe

Quiz Break

24.4 Red shifts
 Doppler
•

effect

Change in the wavelength of light emitted
by an object due to its motion
•

•

Movement away stretches the wavelength
• Longer wavelength
• Light appears redder
Movement toward “squeezes” the wavelength
• Shorter wavelength
• Light shifted toward the blue

24.4 Red shifts (continued)
 Doppler
•

effect

Amount of the Doppler shift indicates the
rate of movement
•
•

Large Doppler shift indicates a high velocity
Small Doppler shift indicates a lower velocity

 Expanding
•

universe

Most galaxies exhibit a red Doppler shift
•

Moving away

Raisin bread analogy of an
expanding universe

Figure 24.24

24.4 Red shifts (continued)
 Expanding
•

universe

Most galaxies exhibit a red Doppler shift
•

•
•
•

Far galaxies
• Exhibit the greatest shift
• Greater velocity
Discovered in 1929 by Edwin Hubble
Hubble's Law – the recessional speed of
galaxies is proportional to their distance
Accounts for red shifts

24.4 Big Bang theory
 Accounts

for galaxies moving away

from us
 Universe was once confined to a "ball"
that was
•
•

•

Supermassive
Dense
Hot

24.4 Big Bang theory (continued)
 Big

Bang marks the inception of the
universe
•
•

Occurred about 15 billion years ago
All matter and space was created

 Matter

is moving outward
 Fate of the universe
•

Two possibilities
•
•

Universe will last forever
Outward expansion sill stop and gravitational;
contraction will follow

24.4 Big Bang theory (continued)
 Fate
•

of the universe

Final fate depends on the average density
of the universe
•
•

If the density is more than the critical density,
then the universe would contract
Current estimates point to less then the critical
density and predict an ever-expanding, or
open, universe

Chapter 24Test Guidance
You will be responsible on the test for answering 3 of the following 6
questions.
1.

2.

3.
4.
5.
6.

What causes the difference between a star’s apparent
magnitude and it absolute magnitude.
List and explain the three factors that control the apparent
brightness of a star as seen from Earth.
Describe how binary stars are used to determine stellar mass.
List and describe the four basic types of galaxies.
What is Hubble’s Law, please explain in detail.
Briefly describe the Big Bang Theory (not the TV show).

End of Chapter 24


Slide 40

Lecture Outlines
PowerPoint

Chapter 24
Earth Science 11e
Tarbuck/Lutgens
Modified for educational
purposes only
By S. Koziol 12-8-2010

© 2006 Pearson Prentice Hall

Earth Science, 11e
Beyond Our
Solar System
Chapter 24

24.1 Properties of stars
 Distance
•
•

Measuring a star's distance can be very
difficult
Stellar parallax
•
•
•

•
•

Used for measuring distance to a star
Apparent shift in a star's position due to the
orbital motion of Earth
Measured as an angle
Near stars have the largest parallax
Largest parallax is less than one second of arc

24. 1 Properties of stars
(continued)

 Distance
•
•

Distances to the stars are very large
Units of measurement
•
•

•

Kilometers or astronomical units are too
cumbersome to use
Light-year is used most often
• Distance that light travels in 1 year
• One light-year is 9.5 trillion km (5.8 trillion
miles)

Other methods for measuring distance are
also used

24. 1 Properties of stars
(continued)

 Stellar
•

Controlled by three factors
•

•
•

•

brightness

Size
Temperature
Distance

Magnitude
•

Measure of a star's brightness

24.1 Properties of stars
(continued)

 Stellar
•

brightness

Magnitude
•

Two types of measurement
• Apparent magnitude
• Brightness when a star is viewed from
Earth
• Decreases with distance
• Numbers are used to designate
magnitudes - dim stars have large
numbers and negative numbers are also
used

24.1 Properties of stars
(continued)

 Stellar
•

brightness

Magnitude
•

Two types of measurement
• Absolute magnitude
• "True" or intrinsic brightness of a star
• Brightness at a standard distance of
32.6 light-years
• Most stars' absolute magnitudes are
between -5 and +15

24.1 Properties of stars
(continued)

 Color
•

Hot star
•

•
•

•

and temperature

Temperature above 30,000 K
Emits short-wavelength light
Appears blue

Cool star
•
•
•

Temperature less than 3000 K
Emits longer-wavelength light
Appears red

24.1 Properties of stars
(continued)

 Color
•

and temperature

Between 5000 and 6000 K
•
•

Stars appear yellow
e.g., Sun

 Binary
•

stars and stellar mass

Binary stars
•

Two stars orbiting one another
• Stars are held together by mutual
gravitation
• Both orbit around a common center of mass

24.1 Properties of stars (continued)
 Binary
•

Binary stars
•

•
•

•

stars and stellar mass

Visual binaries are resolved telescopically
More than 50% of the stars in the universe are
binary stars
Used to determine stellar mass

Stellar mass
•

Determined using binary stars – the center of
mass is closest to the most massive star

Binary stars
orbit each
other around
their common
center of
mass
Figure 24.4

24.1 Properties of stars (continued)
 Binary
•

stars and stellar mass

Stellar mass
•

Mass of most stars is between one-tenth and
fifty times the mass of the Sun

24.1 Hertzsprung-Russell
diagram
 Shows
•
•

the relation between stellar

Brightness (absolute magnitude) and
Temperature

 Diagram

is made by plotting (graphing)
each star's
•
•

Luminosity (brightness) and
Temperature

24.1 Hertzsprung-Russell
diagram (continued)
 Parts
•

Main-sequence stars
•

•
•

•

of an H-R diagram

90% of all stars
Band through the center of the H-R diagram
Sun is in the main-sequence

Giants (or red giants)
•
•
•

Very luminous
Large
Upper-right on the H-R diagram

24.1 Hertzsprung-Russell
diagram (continued)
 Parts
•

Giants (or red giants)
•

•

•

of an H-R diagram

Very large giants are called supergiants
Only a few percent of all stars

White dwarfs
•
•

•
•
•

Fainter than main-sequence stars
Small (approximate the size of Earth)
Lower-central area on the H-R diagram
Not all are white in color
Perhaps 10% of all stars

Idealized HertzsprungRussell diagram

Figure 24.5

Quiz Break

24.2 Variable stars
 Stars

that fluctuate in brightness
 Types of variable stars
•

Pulsating variables
•
•

•

Fluctuate regularly in brightness
Expand and contract in size

Eruptive variables
•
•
•

Explosive event
Sudden brightening
Called a nova

24.2 Interstellar matter
 Between

the stars is "the vacuum of

space"
 Nebula
•
•

Cloud of dust and gases
Two major types of nebulae
•

Bright nebula
• Glows if it close to a very hot star
• Two types of bright nebulae
• Emission nebula
• Reflection nebula

The Orion Nebula is a wellknown emission nebula

Figure 24.8

A faint blue reflection nebula in
the Pleiades star cluster

Figure 24.9

24.2 Interstellar matter (continued)
 Nebula
•

Two major types of nebulae
•

Dark nebula
• Not close to any bright star
• Appear dark
• Contains the material that forms stars and
planets

24.2 Stellar evolution
 Stars

exist because of gravity
 Two opposing forces in a star are
•
•

Gravity – contracts
Thermal nuclear energy – expands

 Stages
•

Birth
•

•
•
•
•

In dark, cool, interstellar clouds
Gravity contracts the cloud
Temperature rises
Radiates long-wavelength (red) light
Becomes a protostar

24.2 Stellar evolution (continued)
 Stages
•

Protostar
•
•
•

•
•
•
•

Gravitational contraction of gaseous cloud
continues
Core reaches 10 million K
Hydrogen nuclei fuse
• Become helium nuclei
• Process is called hydrogen burning
Energy is released
Outward pressure increases
Outward pressure balanced by gravity pulling in
Star becomes a stable main-sequence star

24.2 Stellar evolution (continued)
 Stages
•

Main-sequence stage
•

Stars age at different rates
• Massive stars use fuel faster and exist for
only a few million years
• Small stars use fuel slowly and exist for
perhaps hundreds of billions of years

•

90% of a star's life is in the main-sequence

24.2 Stellar evolution (continued)
 Stages
•

Red giant stage
•
•

•
•
•

Hydrogen burning migrates outward
Star's outer envelope expands
• Surface cools
• Surface becomes red
Core is collapsing as helium is converted to
carbon
Eventually all nuclear fuel is used
Gravity squeezes the star

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Low-mass star
• 0.5 solar mass
• Red giant collapses
• Becomes a white dwarf

24.2 Evolutionary stages of
low mass stars

Figure 24.12 A

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Medium-mass star
• Between 0.5 and 3 solar masses
• Red giant collapses
• Planetary nebula forms
• Becomes a white dwarf

24.2 Evolutionary stages of
medium mass stars

Figure 24.12 B

H-R diagram showing
stellar evolution

Figure 24.11

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Massive star
• Over 3 solar masses
• Short life span
• Terminates in a brilliant explosion called
a supernova
• Interior condenses
• May produce a hot, dense object that is
either a neutron star or a black hole

24.2 Evolutionary stages of
massive stars

Figure 24.12 C

24.2 Stellar remnants
 White
•
•

Small (some no larger than Earth)
Dense
•
•
•

•
•

dwarf

Can be more massive than the Sun
Spoonful weighs several tons
Atoms take up less space
• Electrons displaced inward
• Called degenerate matter

Hot surface
Cools to become a black dwarf

24.2 Stellar remnants (continued)
 Neutron
•

Forms from a more massive star
•
•

•
•

star

Star has more gravity
Squeezes itself smaller

Remnant of a supernova
Gravitational force collapses atoms
•
•

Electrons combine with protons to produce
neutrons
Small size

24.2 Stellar remnants (continued)
 Neutron
•

Pea size sample
•
•

•
•

star

Weighs 100 million tons
Same density as an atomic nucleus

Strong magnetic field
First one discovered in early 1970s
•
•

Pulsar (pulsating radio source)
Found in the Crab nebula (remnant of an A.D.
1054 supernova)

Crab Nebula in the
constellation Taurus

Figure 24.14

24.2 Stellar remnants (continued)
 Black
•
•

•

More dense than a neutron star
Intense surface gravity lets no light escape
As matter is pulled into it
•
•

•

hole

Becomes very hot
Emits x-rays

Likely candidate is Cygnus X-1, a strong xray source

Quiz Break

24.3 Galaxies
 Milky
•

Way galaxy

Structure
•
•

•
•

Determined by using radio telescopes
Large spiral galaxy
• About 100,000 light-years wide
• Thickness at the galactic nucleus is about
10,000 light-years
Three spiral arms of stars
Sun is 30,000 light-years from the center

Face-on view of the
Milk Way Galaxy

Figure 24.18 A

Edge-on view of the
Milk Way Galaxy

Figure 24.18 B

24.3 Galaxies (continued)
 Milky
•

Rotation
•
•
•

•

Way galaxy

Around the galactic nucleus
Outermost stars move the slowest
Sun rotates around the galactic nucleus once
about every 200 million years

Halo surrounds the galactic disk
•
•
•

Spherical
Very tenuous gas
Numerous globular clusters

24.3 Galaxies (continued)
 Other
•
•

galaxies

Existence was first proposed in mid-1700s
by Immanuel Kant
Four basic types of galaxies
•

Spiral galaxy
• Arms extending from nucleus
• About 30% of all galaxies
• Large diameter of 20,000 to 125,000 light
years
• Contains both young and old stars
• e.g., Milky Way

Great Galaxy, a spiral galaxy, in
the constellation Andromeda

Figure 24.20

24.3 Galaxies (continued)
 Other
•

galaxies

Four basic types of galaxies
•

•

Barred spiral galaxy
• Stars arranged in the shape of a bar
• Generally quite large
• About 10% of all galaxies
Elliptical galaxy
• Ellipsoidal shape
• About 60% of all galaxies
• Most are smaller than spiral galaxies;
however, they are also the largest known
galaxies

A barred spiral galaxy

Figure 24.22

24.3 Galaxies (continued)
 Other
•

galaxies

Four basic types of galaxies
•

Irregular galaxy
• Lacks symmetry
• About 10% of all galaxies
• Contains mostly young stars
• e.g., Magellanic Clouds

24.3 Galaxies (continued)
 Galactic
•
•
•

Group of galaxies
Some contain thousands of galaxies
Local Group
•
•

•

cluster

Our own group of galaxies
Contains at least 28 galaxies

Supercluster
•
•

Huge swarm of galaxies
May be the largest entity in the universe

Quiz Break

24.4 Red shifts
 Doppler
•

effect

Change in the wavelength of light emitted
by an object due to its motion
•

•

Movement away stretches the wavelength
• Longer wavelength
• Light appears redder
Movement toward “squeezes” the wavelength
• Shorter wavelength
• Light shifted toward the blue

24.4 Red shifts (continued)
 Doppler
•

effect

Amount of the Doppler shift indicates the
rate of movement
•
•

Large Doppler shift indicates a high velocity
Small Doppler shift indicates a lower velocity

 Expanding
•

universe

Most galaxies exhibit a red Doppler shift
•

Moving away

Raisin bread analogy of an
expanding universe

Figure 24.24

24.4 Red shifts (continued)
 Expanding
•

universe

Most galaxies exhibit a red Doppler shift
•

•
•
•

Far galaxies
• Exhibit the greatest shift
• Greater velocity
Discovered in 1929 by Edwin Hubble
Hubble's Law – the recessional speed of
galaxies is proportional to their distance
Accounts for red shifts

24.4 Big Bang theory
 Accounts

for galaxies moving away

from us
 Universe was once confined to a "ball"
that was
•
•

•

Supermassive
Dense
Hot

24.4 Big Bang theory (continued)
 Big

Bang marks the inception of the
universe
•
•

Occurred about 15 billion years ago
All matter and space was created

 Matter

is moving outward
 Fate of the universe
•

Two possibilities
•
•

Universe will last forever
Outward expansion sill stop and gravitational;
contraction will follow

24.4 Big Bang theory (continued)
 Fate
•

of the universe

Final fate depends on the average density
of the universe
•
•

If the density is more than the critical density,
then the universe would contract
Current estimates point to less then the critical
density and predict an ever-expanding, or
open, universe

Chapter 24Test Guidance
You will be responsible on the test for answering 3 of the following 6
questions.
1.

2.

3.
4.
5.
6.

What causes the difference between a star’s apparent
magnitude and it absolute magnitude.
List and explain the three factors that control the apparent
brightness of a star as seen from Earth.
Describe how binary stars are used to determine stellar mass.
List and describe the four basic types of galaxies.
What is Hubble’s Law, please explain in detail.
Briefly describe the Big Bang Theory (not the TV show).

End of Chapter 24


Slide 41

Lecture Outlines
PowerPoint

Chapter 24
Earth Science 11e
Tarbuck/Lutgens
Modified for educational
purposes only
By S. Koziol 12-8-2010

© 2006 Pearson Prentice Hall

Earth Science, 11e
Beyond Our
Solar System
Chapter 24

24.1 Properties of stars
 Distance
•
•

Measuring a star's distance can be very
difficult
Stellar parallax
•
•
•

•
•

Used for measuring distance to a star
Apparent shift in a star's position due to the
orbital motion of Earth
Measured as an angle
Near stars have the largest parallax
Largest parallax is less than one second of arc

24. 1 Properties of stars
(continued)

 Distance
•
•

Distances to the stars are very large
Units of measurement
•
•

•

Kilometers or astronomical units are too
cumbersome to use
Light-year is used most often
• Distance that light travels in 1 year
• One light-year is 9.5 trillion km (5.8 trillion
miles)

Other methods for measuring distance are
also used

24. 1 Properties of stars
(continued)

 Stellar
•

Controlled by three factors
•

•
•

•

brightness

Size
Temperature
Distance

Magnitude
•

Measure of a star's brightness

24.1 Properties of stars
(continued)

 Stellar
•

brightness

Magnitude
•

Two types of measurement
• Apparent magnitude
• Brightness when a star is viewed from
Earth
• Decreases with distance
• Numbers are used to designate
magnitudes - dim stars have large
numbers and negative numbers are also
used

24.1 Properties of stars
(continued)

 Stellar
•

brightness

Magnitude
•

Two types of measurement
• Absolute magnitude
• "True" or intrinsic brightness of a star
• Brightness at a standard distance of
32.6 light-years
• Most stars' absolute magnitudes are
between -5 and +15

24.1 Properties of stars
(continued)

 Color
•

Hot star
•

•
•

•

and temperature

Temperature above 30,000 K
Emits short-wavelength light
Appears blue

Cool star
•
•
•

Temperature less than 3000 K
Emits longer-wavelength light
Appears red

24.1 Properties of stars
(continued)

 Color
•

and temperature

Between 5000 and 6000 K
•
•

Stars appear yellow
e.g., Sun

 Binary
•

stars and stellar mass

Binary stars
•

Two stars orbiting one another
• Stars are held together by mutual
gravitation
• Both orbit around a common center of mass

24.1 Properties of stars (continued)
 Binary
•

Binary stars
•

•
•

•

stars and stellar mass

Visual binaries are resolved telescopically
More than 50% of the stars in the universe are
binary stars
Used to determine stellar mass

Stellar mass
•

Determined using binary stars – the center of
mass is closest to the most massive star

Binary stars
orbit each
other around
their common
center of
mass
Figure 24.4

24.1 Properties of stars (continued)
 Binary
•

stars and stellar mass

Stellar mass
•

Mass of most stars is between one-tenth and
fifty times the mass of the Sun

24.1 Hertzsprung-Russell
diagram
 Shows
•
•

the relation between stellar

Brightness (absolute magnitude) and
Temperature

 Diagram

is made by plotting (graphing)
each star's
•
•

Luminosity (brightness) and
Temperature

24.1 Hertzsprung-Russell
diagram (continued)
 Parts
•

Main-sequence stars
•

•
•

•

of an H-R diagram

90% of all stars
Band through the center of the H-R diagram
Sun is in the main-sequence

Giants (or red giants)
•
•
•

Very luminous
Large
Upper-right on the H-R diagram

24.1 Hertzsprung-Russell
diagram (continued)
 Parts
•

Giants (or red giants)
•

•

•

of an H-R diagram

Very large giants are called supergiants
Only a few percent of all stars

White dwarfs
•
•

•
•
•

Fainter than main-sequence stars
Small (approximate the size of Earth)
Lower-central area on the H-R diagram
Not all are white in color
Perhaps 10% of all stars

Idealized HertzsprungRussell diagram

Figure 24.5

Quiz Break

24.2 Variable stars
 Stars

that fluctuate in brightness
 Types of variable stars
•

Pulsating variables
•
•

•

Fluctuate regularly in brightness
Expand and contract in size

Eruptive variables
•
•
•

Explosive event
Sudden brightening
Called a nova

24.2 Interstellar matter
 Between

the stars is "the vacuum of

space"
 Nebula
•
•

Cloud of dust and gases
Two major types of nebulae
•

Bright nebula
• Glows if it close to a very hot star
• Two types of bright nebulae
• Emission nebula
• Reflection nebula

The Orion Nebula is a wellknown emission nebula

Figure 24.8

A faint blue reflection nebula in
the Pleiades star cluster

Figure 24.9

24.2 Interstellar matter (continued)
 Nebula
•

Two major types of nebulae
•

Dark nebula
• Not close to any bright star
• Appear dark
• Contains the material that forms stars and
planets

24.2 Stellar evolution
 Stars

exist because of gravity
 Two opposing forces in a star are
•
•

Gravity – contracts
Thermal nuclear energy – expands

 Stages
•

Birth
•

•
•
•
•

In dark, cool, interstellar clouds
Gravity contracts the cloud
Temperature rises
Radiates long-wavelength (red) light
Becomes a protostar

24.2 Stellar evolution (continued)
 Stages
•

Protostar
•
•
•

•
•
•
•

Gravitational contraction of gaseous cloud
continues
Core reaches 10 million K
Hydrogen nuclei fuse
• Become helium nuclei
• Process is called hydrogen burning
Energy is released
Outward pressure increases
Outward pressure balanced by gravity pulling in
Star becomes a stable main-sequence star

24.2 Stellar evolution (continued)
 Stages
•

Main-sequence stage
•

Stars age at different rates
• Massive stars use fuel faster and exist for
only a few million years
• Small stars use fuel slowly and exist for
perhaps hundreds of billions of years

•

90% of a star's life is in the main-sequence

24.2 Stellar evolution (continued)
 Stages
•

Red giant stage
•
•

•
•
•

Hydrogen burning migrates outward
Star's outer envelope expands
• Surface cools
• Surface becomes red
Core is collapsing as helium is converted to
carbon
Eventually all nuclear fuel is used
Gravity squeezes the star

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Low-mass star
• 0.5 solar mass
• Red giant collapses
• Becomes a white dwarf

24.2 Evolutionary stages of
low mass stars

Figure 24.12 A

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Medium-mass star
• Between 0.5 and 3 solar masses
• Red giant collapses
• Planetary nebula forms
• Becomes a white dwarf

24.2 Evolutionary stages of
medium mass stars

Figure 24.12 B

H-R diagram showing
stellar evolution

Figure 24.11

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Massive star
• Over 3 solar masses
• Short life span
• Terminates in a brilliant explosion called
a supernova
• Interior condenses
• May produce a hot, dense object that is
either a neutron star or a black hole

24.2 Evolutionary stages of
massive stars

Figure 24.12 C

24.2 Stellar remnants
 White
•
•

Small (some no larger than Earth)
Dense
•
•
•

•
•

dwarf

Can be more massive than the Sun
Spoonful weighs several tons
Atoms take up less space
• Electrons displaced inward
• Called degenerate matter

Hot surface
Cools to become a black dwarf

24.2 Stellar remnants (continued)
 Neutron
•

Forms from a more massive star
•
•

•
•

star

Star has more gravity
Squeezes itself smaller

Remnant of a supernova
Gravitational force collapses atoms
•
•

Electrons combine with protons to produce
neutrons
Small size

24.2 Stellar remnants (continued)
 Neutron
•

Pea size sample
•
•

•
•

star

Weighs 100 million tons
Same density as an atomic nucleus

Strong magnetic field
First one discovered in early 1970s
•
•

Pulsar (pulsating radio source)
Found in the Crab nebula (remnant of an A.D.
1054 supernova)

Crab Nebula in the
constellation Taurus

Figure 24.14

24.2 Stellar remnants (continued)
 Black
•
•

•

More dense than a neutron star
Intense surface gravity lets no light escape
As matter is pulled into it
•
•

•

hole

Becomes very hot
Emits x-rays

Likely candidate is Cygnus X-1, a strong xray source

Quiz Break

24.3 Galaxies
 Milky
•

Way galaxy

Structure
•
•

•
•

Determined by using radio telescopes
Large spiral galaxy
• About 100,000 light-years wide
• Thickness at the galactic nucleus is about
10,000 light-years
Three spiral arms of stars
Sun is 30,000 light-years from the center

Face-on view of the
Milk Way Galaxy

Figure 24.18 A

Edge-on view of the
Milk Way Galaxy

Figure 24.18 B

24.3 Galaxies (continued)
 Milky
•

Rotation
•
•
•

•

Way galaxy

Around the galactic nucleus
Outermost stars move the slowest
Sun rotates around the galactic nucleus once
about every 200 million years

Halo surrounds the galactic disk
•
•
•

Spherical
Very tenuous gas
Numerous globular clusters

24.3 Galaxies (continued)
 Other
•
•

galaxies

Existence was first proposed in mid-1700s
by Immanuel Kant
Four basic types of galaxies
•

Spiral galaxy
• Arms extending from nucleus
• About 30% of all galaxies
• Large diameter of 20,000 to 125,000 light
years
• Contains both young and old stars
• e.g., Milky Way

Great Galaxy, a spiral galaxy, in
the constellation Andromeda

Figure 24.20

24.3 Galaxies (continued)
 Other
•

galaxies

Four basic types of galaxies
•

•

Barred spiral galaxy
• Stars arranged in the shape of a bar
• Generally quite large
• About 10% of all galaxies
Elliptical galaxy
• Ellipsoidal shape
• About 60% of all galaxies
• Most are smaller than spiral galaxies;
however, they are also the largest known
galaxies

A barred spiral galaxy

Figure 24.22

24.3 Galaxies (continued)
 Other
•

galaxies

Four basic types of galaxies
•

Irregular galaxy
• Lacks symmetry
• About 10% of all galaxies
• Contains mostly young stars
• e.g., Magellanic Clouds

24.3 Galaxies (continued)
 Galactic
•
•
•

Group of galaxies
Some contain thousands of galaxies
Local Group
•
•

•

cluster

Our own group of galaxies
Contains at least 28 galaxies

Supercluster
•
•

Huge swarm of galaxies
May be the largest entity in the universe

Quiz Break

24.4 Red shifts
 Doppler
•

effect

Change in the wavelength of light emitted
by an object due to its motion
•

•

Movement away stretches the wavelength
• Longer wavelength
• Light appears redder
Movement toward “squeezes” the wavelength
• Shorter wavelength
• Light shifted toward the blue

24.4 Red shifts (continued)
 Doppler
•

effect

Amount of the Doppler shift indicates the
rate of movement
•
•

Large Doppler shift indicates a high velocity
Small Doppler shift indicates a lower velocity

 Expanding
•

universe

Most galaxies exhibit a red Doppler shift
•

Moving away

Raisin bread analogy of an
expanding universe

Figure 24.24

24.4 Red shifts (continued)
 Expanding
•

universe

Most galaxies exhibit a red Doppler shift
•

•
•
•

Far galaxies
• Exhibit the greatest shift
• Greater velocity
Discovered in 1929 by Edwin Hubble
Hubble's Law – the recessional speed of
galaxies is proportional to their distance
Accounts for red shifts

24.4 Big Bang theory
 Accounts

for galaxies moving away

from us
 Universe was once confined to a "ball"
that was
•
•

•

Supermassive
Dense
Hot

24.4 Big Bang theory (continued)
 Big

Bang marks the inception of the
universe
•
•

Occurred about 15 billion years ago
All matter and space was created

 Matter

is moving outward
 Fate of the universe
•

Two possibilities
•
•

Universe will last forever
Outward expansion sill stop and gravitational;
contraction will follow

24.4 Big Bang theory (continued)
 Fate
•

of the universe

Final fate depends on the average density
of the universe
•
•

If the density is more than the critical density,
then the universe would contract
Current estimates point to less then the critical
density and predict an ever-expanding, or
open, universe

Chapter 24Test Guidance
You will be responsible on the test for answering 3 of the following 6
questions.
1.

2.

3.
4.
5.
6.

What causes the difference between a star’s apparent
magnitude and it absolute magnitude.
List and explain the three factors that control the apparent
brightness of a star as seen from Earth.
Describe how binary stars are used to determine stellar mass.
List and describe the four basic types of galaxies.
What is Hubble’s Law, please explain in detail.
Briefly describe the Big Bang Theory (not the TV show).

End of Chapter 24


Slide 42

Lecture Outlines
PowerPoint

Chapter 24
Earth Science 11e
Tarbuck/Lutgens
Modified for educational
purposes only
By S. Koziol 12-8-2010

© 2006 Pearson Prentice Hall

Earth Science, 11e
Beyond Our
Solar System
Chapter 24

24.1 Properties of stars
 Distance
•
•

Measuring a star's distance can be very
difficult
Stellar parallax
•
•
•

•
•

Used for measuring distance to a star
Apparent shift in a star's position due to the
orbital motion of Earth
Measured as an angle
Near stars have the largest parallax
Largest parallax is less than one second of arc

24. 1 Properties of stars
(continued)

 Distance
•
•

Distances to the stars are very large
Units of measurement
•
•

•

Kilometers or astronomical units are too
cumbersome to use
Light-year is used most often
• Distance that light travels in 1 year
• One light-year is 9.5 trillion km (5.8 trillion
miles)

Other methods for measuring distance are
also used

24. 1 Properties of stars
(continued)

 Stellar
•

Controlled by three factors
•

•
•

•

brightness

Size
Temperature
Distance

Magnitude
•

Measure of a star's brightness

24.1 Properties of stars
(continued)

 Stellar
•

brightness

Magnitude
•

Two types of measurement
• Apparent magnitude
• Brightness when a star is viewed from
Earth
• Decreases with distance
• Numbers are used to designate
magnitudes - dim stars have large
numbers and negative numbers are also
used

24.1 Properties of stars
(continued)

 Stellar
•

brightness

Magnitude
•

Two types of measurement
• Absolute magnitude
• "True" or intrinsic brightness of a star
• Brightness at a standard distance of
32.6 light-years
• Most stars' absolute magnitudes are
between -5 and +15

24.1 Properties of stars
(continued)

 Color
•

Hot star
•

•
•

•

and temperature

Temperature above 30,000 K
Emits short-wavelength light
Appears blue

Cool star
•
•
•

Temperature less than 3000 K
Emits longer-wavelength light
Appears red

24.1 Properties of stars
(continued)

 Color
•

and temperature

Between 5000 and 6000 K
•
•

Stars appear yellow
e.g., Sun

 Binary
•

stars and stellar mass

Binary stars
•

Two stars orbiting one another
• Stars are held together by mutual
gravitation
• Both orbit around a common center of mass

24.1 Properties of stars (continued)
 Binary
•

Binary stars
•

•
•

•

stars and stellar mass

Visual binaries are resolved telescopically
More than 50% of the stars in the universe are
binary stars
Used to determine stellar mass

Stellar mass
•

Determined using binary stars – the center of
mass is closest to the most massive star

Binary stars
orbit each
other around
their common
center of
mass
Figure 24.4

24.1 Properties of stars (continued)
 Binary
•

stars and stellar mass

Stellar mass
•

Mass of most stars is between one-tenth and
fifty times the mass of the Sun

24.1 Hertzsprung-Russell
diagram
 Shows
•
•

the relation between stellar

Brightness (absolute magnitude) and
Temperature

 Diagram

is made by plotting (graphing)
each star's
•
•

Luminosity (brightness) and
Temperature

24.1 Hertzsprung-Russell
diagram (continued)
 Parts
•

Main-sequence stars
•

•
•

•

of an H-R diagram

90% of all stars
Band through the center of the H-R diagram
Sun is in the main-sequence

Giants (or red giants)
•
•
•

Very luminous
Large
Upper-right on the H-R diagram

24.1 Hertzsprung-Russell
diagram (continued)
 Parts
•

Giants (or red giants)
•

•

•

of an H-R diagram

Very large giants are called supergiants
Only a few percent of all stars

White dwarfs
•
•

•
•
•

Fainter than main-sequence stars
Small (approximate the size of Earth)
Lower-central area on the H-R diagram
Not all are white in color
Perhaps 10% of all stars

Idealized HertzsprungRussell diagram

Figure 24.5

Quiz Break

24.2 Variable stars
 Stars

that fluctuate in brightness
 Types of variable stars
•

Pulsating variables
•
•

•

Fluctuate regularly in brightness
Expand and contract in size

Eruptive variables
•
•
•

Explosive event
Sudden brightening
Called a nova

24.2 Interstellar matter
 Between

the stars is "the vacuum of

space"
 Nebula
•
•

Cloud of dust and gases
Two major types of nebulae
•

Bright nebula
• Glows if it close to a very hot star
• Two types of bright nebulae
• Emission nebula
• Reflection nebula

The Orion Nebula is a wellknown emission nebula

Figure 24.8

A faint blue reflection nebula in
the Pleiades star cluster

Figure 24.9

24.2 Interstellar matter (continued)
 Nebula
•

Two major types of nebulae
•

Dark nebula
• Not close to any bright star
• Appear dark
• Contains the material that forms stars and
planets

24.2 Stellar evolution
 Stars

exist because of gravity
 Two opposing forces in a star are
•
•

Gravity – contracts
Thermal nuclear energy – expands

 Stages
•

Birth
•

•
•
•
•

In dark, cool, interstellar clouds
Gravity contracts the cloud
Temperature rises
Radiates long-wavelength (red) light
Becomes a protostar

24.2 Stellar evolution (continued)
 Stages
•

Protostar
•
•
•

•
•
•
•

Gravitational contraction of gaseous cloud
continues
Core reaches 10 million K
Hydrogen nuclei fuse
• Become helium nuclei
• Process is called hydrogen burning
Energy is released
Outward pressure increases
Outward pressure balanced by gravity pulling in
Star becomes a stable main-sequence star

24.2 Stellar evolution (continued)
 Stages
•

Main-sequence stage
•

Stars age at different rates
• Massive stars use fuel faster and exist for
only a few million years
• Small stars use fuel slowly and exist for
perhaps hundreds of billions of years

•

90% of a star's life is in the main-sequence

24.2 Stellar evolution (continued)
 Stages
•

Red giant stage
•
•

•
•
•

Hydrogen burning migrates outward
Star's outer envelope expands
• Surface cools
• Surface becomes red
Core is collapsing as helium is converted to
carbon
Eventually all nuclear fuel is used
Gravity squeezes the star

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Low-mass star
• 0.5 solar mass
• Red giant collapses
• Becomes a white dwarf

24.2 Evolutionary stages of
low mass stars

Figure 24.12 A

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Medium-mass star
• Between 0.5 and 3 solar masses
• Red giant collapses
• Planetary nebula forms
• Becomes a white dwarf

24.2 Evolutionary stages of
medium mass stars

Figure 24.12 B

H-R diagram showing
stellar evolution

Figure 24.11

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Massive star
• Over 3 solar masses
• Short life span
• Terminates in a brilliant explosion called
a supernova
• Interior condenses
• May produce a hot, dense object that is
either a neutron star or a black hole

24.2 Evolutionary stages of
massive stars

Figure 24.12 C

24.2 Stellar remnants
 White
•
•

Small (some no larger than Earth)
Dense
•
•
•

•
•

dwarf

Can be more massive than the Sun
Spoonful weighs several tons
Atoms take up less space
• Electrons displaced inward
• Called degenerate matter

Hot surface
Cools to become a black dwarf

24.2 Stellar remnants (continued)
 Neutron
•

Forms from a more massive star
•
•

•
•

star

Star has more gravity
Squeezes itself smaller

Remnant of a supernova
Gravitational force collapses atoms
•
•

Electrons combine with protons to produce
neutrons
Small size

24.2 Stellar remnants (continued)
 Neutron
•

Pea size sample
•
•

•
•

star

Weighs 100 million tons
Same density as an atomic nucleus

Strong magnetic field
First one discovered in early 1970s
•
•

Pulsar (pulsating radio source)
Found in the Crab nebula (remnant of an A.D.
1054 supernova)

Crab Nebula in the
constellation Taurus

Figure 24.14

24.2 Stellar remnants (continued)
 Black
•
•

•

More dense than a neutron star
Intense surface gravity lets no light escape
As matter is pulled into it
•
•

•

hole

Becomes very hot
Emits x-rays

Likely candidate is Cygnus X-1, a strong xray source

Quiz Break

24.3 Galaxies
 Milky
•

Way galaxy

Structure
•
•

•
•

Determined by using radio telescopes
Large spiral galaxy
• About 100,000 light-years wide
• Thickness at the galactic nucleus is about
10,000 light-years
Three spiral arms of stars
Sun is 30,000 light-years from the center

Face-on view of the
Milk Way Galaxy

Figure 24.18 A

Edge-on view of the
Milk Way Galaxy

Figure 24.18 B

24.3 Galaxies (continued)
 Milky
•

Rotation
•
•
•

•

Way galaxy

Around the galactic nucleus
Outermost stars move the slowest
Sun rotates around the galactic nucleus once
about every 200 million years

Halo surrounds the galactic disk
•
•
•

Spherical
Very tenuous gas
Numerous globular clusters

24.3 Galaxies (continued)
 Other
•
•

galaxies

Existence was first proposed in mid-1700s
by Immanuel Kant
Four basic types of galaxies
•

Spiral galaxy
• Arms extending from nucleus
• About 30% of all galaxies
• Large diameter of 20,000 to 125,000 light
years
• Contains both young and old stars
• e.g., Milky Way

Great Galaxy, a spiral galaxy, in
the constellation Andromeda

Figure 24.20

24.3 Galaxies (continued)
 Other
•

galaxies

Four basic types of galaxies
•

•

Barred spiral galaxy
• Stars arranged in the shape of a bar
• Generally quite large
• About 10% of all galaxies
Elliptical galaxy
• Ellipsoidal shape
• About 60% of all galaxies
• Most are smaller than spiral galaxies;
however, they are also the largest known
galaxies

A barred spiral galaxy

Figure 24.22

24.3 Galaxies (continued)
 Other
•

galaxies

Four basic types of galaxies
•

Irregular galaxy
• Lacks symmetry
• About 10% of all galaxies
• Contains mostly young stars
• e.g., Magellanic Clouds

24.3 Galaxies (continued)
 Galactic
•
•
•

Group of galaxies
Some contain thousands of galaxies
Local Group
•
•

•

cluster

Our own group of galaxies
Contains at least 28 galaxies

Supercluster
•
•

Huge swarm of galaxies
May be the largest entity in the universe

Quiz Break

24.4 Red shifts
 Doppler
•

effect

Change in the wavelength of light emitted
by an object due to its motion
•

•

Movement away stretches the wavelength
• Longer wavelength
• Light appears redder
Movement toward “squeezes” the wavelength
• Shorter wavelength
• Light shifted toward the blue

24.4 Red shifts (continued)
 Doppler
•

effect

Amount of the Doppler shift indicates the
rate of movement
•
•

Large Doppler shift indicates a high velocity
Small Doppler shift indicates a lower velocity

 Expanding
•

universe

Most galaxies exhibit a red Doppler shift
•

Moving away

Raisin bread analogy of an
expanding universe

Figure 24.24

24.4 Red shifts (continued)
 Expanding
•

universe

Most galaxies exhibit a red Doppler shift
•

•
•
•

Far galaxies
• Exhibit the greatest shift
• Greater velocity
Discovered in 1929 by Edwin Hubble
Hubble's Law – the recessional speed of
galaxies is proportional to their distance
Accounts for red shifts

24.4 Big Bang theory
 Accounts

for galaxies moving away

from us
 Universe was once confined to a "ball"
that was
•
•

•

Supermassive
Dense
Hot

24.4 Big Bang theory (continued)
 Big

Bang marks the inception of the
universe
•
•

Occurred about 15 billion years ago
All matter and space was created

 Matter

is moving outward
 Fate of the universe
•

Two possibilities
•
•

Universe will last forever
Outward expansion sill stop and gravitational;
contraction will follow

24.4 Big Bang theory (continued)
 Fate
•

of the universe

Final fate depends on the average density
of the universe
•
•

If the density is more than the critical density,
then the universe would contract
Current estimates point to less then the critical
density and predict an ever-expanding, or
open, universe

Chapter 24Test Guidance
You will be responsible on the test for answering 3 of the following 6
questions.
1.

2.

3.
4.
5.
6.

What causes the difference between a star’s apparent
magnitude and it absolute magnitude.
List and explain the three factors that control the apparent
brightness of a star as seen from Earth.
Describe how binary stars are used to determine stellar mass.
List and describe the four basic types of galaxies.
What is Hubble’s Law, please explain in detail.
Briefly describe the Big Bang Theory (not the TV show).

End of Chapter 24


Slide 43

Lecture Outlines
PowerPoint

Chapter 24
Earth Science 11e
Tarbuck/Lutgens
Modified for educational
purposes only
By S. Koziol 12-8-2010

© 2006 Pearson Prentice Hall

Earth Science, 11e
Beyond Our
Solar System
Chapter 24

24.1 Properties of stars
 Distance
•
•

Measuring a star's distance can be very
difficult
Stellar parallax
•
•
•

•
•

Used for measuring distance to a star
Apparent shift in a star's position due to the
orbital motion of Earth
Measured as an angle
Near stars have the largest parallax
Largest parallax is less than one second of arc

24. 1 Properties of stars
(continued)

 Distance
•
•

Distances to the stars are very large
Units of measurement
•
•

•

Kilometers or astronomical units are too
cumbersome to use
Light-year is used most often
• Distance that light travels in 1 year
• One light-year is 9.5 trillion km (5.8 trillion
miles)

Other methods for measuring distance are
also used

24. 1 Properties of stars
(continued)

 Stellar
•

Controlled by three factors
•

•
•

•

brightness

Size
Temperature
Distance

Magnitude
•

Measure of a star's brightness

24.1 Properties of stars
(continued)

 Stellar
•

brightness

Magnitude
•

Two types of measurement
• Apparent magnitude
• Brightness when a star is viewed from
Earth
• Decreases with distance
• Numbers are used to designate
magnitudes - dim stars have large
numbers and negative numbers are also
used

24.1 Properties of stars
(continued)

 Stellar
•

brightness

Magnitude
•

Two types of measurement
• Absolute magnitude
• "True" or intrinsic brightness of a star
• Brightness at a standard distance of
32.6 light-years
• Most stars' absolute magnitudes are
between -5 and +15

24.1 Properties of stars
(continued)

 Color
•

Hot star
•

•
•

•

and temperature

Temperature above 30,000 K
Emits short-wavelength light
Appears blue

Cool star
•
•
•

Temperature less than 3000 K
Emits longer-wavelength light
Appears red

24.1 Properties of stars
(continued)

 Color
•

and temperature

Between 5000 and 6000 K
•
•

Stars appear yellow
e.g., Sun

 Binary
•

stars and stellar mass

Binary stars
•

Two stars orbiting one another
• Stars are held together by mutual
gravitation
• Both orbit around a common center of mass

24.1 Properties of stars (continued)
 Binary
•

Binary stars
•

•
•

•

stars and stellar mass

Visual binaries are resolved telescopically
More than 50% of the stars in the universe are
binary stars
Used to determine stellar mass

Stellar mass
•

Determined using binary stars – the center of
mass is closest to the most massive star

Binary stars
orbit each
other around
their common
center of
mass
Figure 24.4

24.1 Properties of stars (continued)
 Binary
•

stars and stellar mass

Stellar mass
•

Mass of most stars is between one-tenth and
fifty times the mass of the Sun

24.1 Hertzsprung-Russell
diagram
 Shows
•
•

the relation between stellar

Brightness (absolute magnitude) and
Temperature

 Diagram

is made by plotting (graphing)
each star's
•
•

Luminosity (brightness) and
Temperature

24.1 Hertzsprung-Russell
diagram (continued)
 Parts
•

Main-sequence stars
•

•
•

•

of an H-R diagram

90% of all stars
Band through the center of the H-R diagram
Sun is in the main-sequence

Giants (or red giants)
•
•
•

Very luminous
Large
Upper-right on the H-R diagram

24.1 Hertzsprung-Russell
diagram (continued)
 Parts
•

Giants (or red giants)
•

•

•

of an H-R diagram

Very large giants are called supergiants
Only a few percent of all stars

White dwarfs
•
•

•
•
•

Fainter than main-sequence stars
Small (approximate the size of Earth)
Lower-central area on the H-R diagram
Not all are white in color
Perhaps 10% of all stars

Idealized HertzsprungRussell diagram

Figure 24.5

Quiz Break

24.2 Variable stars
 Stars

that fluctuate in brightness
 Types of variable stars
•

Pulsating variables
•
•

•

Fluctuate regularly in brightness
Expand and contract in size

Eruptive variables
•
•
•

Explosive event
Sudden brightening
Called a nova

24.2 Interstellar matter
 Between

the stars is "the vacuum of

space"
 Nebula
•
•

Cloud of dust and gases
Two major types of nebulae
•

Bright nebula
• Glows if it close to a very hot star
• Two types of bright nebulae
• Emission nebula
• Reflection nebula

The Orion Nebula is a wellknown emission nebula

Figure 24.8

A faint blue reflection nebula in
the Pleiades star cluster

Figure 24.9

24.2 Interstellar matter (continued)
 Nebula
•

Two major types of nebulae
•

Dark nebula
• Not close to any bright star
• Appear dark
• Contains the material that forms stars and
planets

24.2 Stellar evolution
 Stars

exist because of gravity
 Two opposing forces in a star are
•
•

Gravity – contracts
Thermal nuclear energy – expands

 Stages
•

Birth
•

•
•
•
•

In dark, cool, interstellar clouds
Gravity contracts the cloud
Temperature rises
Radiates long-wavelength (red) light
Becomes a protostar

24.2 Stellar evolution (continued)
 Stages
•

Protostar
•
•
•

•
•
•
•

Gravitational contraction of gaseous cloud
continues
Core reaches 10 million K
Hydrogen nuclei fuse
• Become helium nuclei
• Process is called hydrogen burning
Energy is released
Outward pressure increases
Outward pressure balanced by gravity pulling in
Star becomes a stable main-sequence star

24.2 Stellar evolution (continued)
 Stages
•

Main-sequence stage
•

Stars age at different rates
• Massive stars use fuel faster and exist for
only a few million years
• Small stars use fuel slowly and exist for
perhaps hundreds of billions of years

•

90% of a star's life is in the main-sequence

24.2 Stellar evolution (continued)
 Stages
•

Red giant stage
•
•

•
•
•

Hydrogen burning migrates outward
Star's outer envelope expands
• Surface cools
• Surface becomes red
Core is collapsing as helium is converted to
carbon
Eventually all nuclear fuel is used
Gravity squeezes the star

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Low-mass star
• 0.5 solar mass
• Red giant collapses
• Becomes a white dwarf

24.2 Evolutionary stages of
low mass stars

Figure 24.12 A

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Medium-mass star
• Between 0.5 and 3 solar masses
• Red giant collapses
• Planetary nebula forms
• Becomes a white dwarf

24.2 Evolutionary stages of
medium mass stars

Figure 24.12 B

H-R diagram showing
stellar evolution

Figure 24.11

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Massive star
• Over 3 solar masses
• Short life span
• Terminates in a brilliant explosion called
a supernova
• Interior condenses
• May produce a hot, dense object that is
either a neutron star or a black hole

24.2 Evolutionary stages of
massive stars

Figure 24.12 C

24.2 Stellar remnants
 White
•
•

Small (some no larger than Earth)
Dense
•
•
•

•
•

dwarf

Can be more massive than the Sun
Spoonful weighs several tons
Atoms take up less space
• Electrons displaced inward
• Called degenerate matter

Hot surface
Cools to become a black dwarf

24.2 Stellar remnants (continued)
 Neutron
•

Forms from a more massive star
•
•

•
•

star

Star has more gravity
Squeezes itself smaller

Remnant of a supernova
Gravitational force collapses atoms
•
•

Electrons combine with protons to produce
neutrons
Small size

24.2 Stellar remnants (continued)
 Neutron
•

Pea size sample
•
•

•
•

star

Weighs 100 million tons
Same density as an atomic nucleus

Strong magnetic field
First one discovered in early 1970s
•
•

Pulsar (pulsating radio source)
Found in the Crab nebula (remnant of an A.D.
1054 supernova)

Crab Nebula in the
constellation Taurus

Figure 24.14

24.2 Stellar remnants (continued)
 Black
•
•

•

More dense than a neutron star
Intense surface gravity lets no light escape
As matter is pulled into it
•
•

•

hole

Becomes very hot
Emits x-rays

Likely candidate is Cygnus X-1, a strong xray source

Quiz Break

24.3 Galaxies
 Milky
•

Way galaxy

Structure
•
•

•
•

Determined by using radio telescopes
Large spiral galaxy
• About 100,000 light-years wide
• Thickness at the galactic nucleus is about
10,000 light-years
Three spiral arms of stars
Sun is 30,000 light-years from the center

Face-on view of the
Milk Way Galaxy

Figure 24.18 A

Edge-on view of the
Milk Way Galaxy

Figure 24.18 B

24.3 Galaxies (continued)
 Milky
•

Rotation
•
•
•

•

Way galaxy

Around the galactic nucleus
Outermost stars move the slowest
Sun rotates around the galactic nucleus once
about every 200 million years

Halo surrounds the galactic disk
•
•
•

Spherical
Very tenuous gas
Numerous globular clusters

24.3 Galaxies (continued)
 Other
•
•

galaxies

Existence was first proposed in mid-1700s
by Immanuel Kant
Four basic types of galaxies
•

Spiral galaxy
• Arms extending from nucleus
• About 30% of all galaxies
• Large diameter of 20,000 to 125,000 light
years
• Contains both young and old stars
• e.g., Milky Way

Great Galaxy, a spiral galaxy, in
the constellation Andromeda

Figure 24.20

24.3 Galaxies (continued)
 Other
•

galaxies

Four basic types of galaxies
•

•

Barred spiral galaxy
• Stars arranged in the shape of a bar
• Generally quite large
• About 10% of all galaxies
Elliptical galaxy
• Ellipsoidal shape
• About 60% of all galaxies
• Most are smaller than spiral galaxies;
however, they are also the largest known
galaxies

A barred spiral galaxy

Figure 24.22

24.3 Galaxies (continued)
 Other
•

galaxies

Four basic types of galaxies
•

Irregular galaxy
• Lacks symmetry
• About 10% of all galaxies
• Contains mostly young stars
• e.g., Magellanic Clouds

24.3 Galaxies (continued)
 Galactic
•
•
•

Group of galaxies
Some contain thousands of galaxies
Local Group
•
•

•

cluster

Our own group of galaxies
Contains at least 28 galaxies

Supercluster
•
•

Huge swarm of galaxies
May be the largest entity in the universe

Quiz Break

24.4 Red shifts
 Doppler
•

effect

Change in the wavelength of light emitted
by an object due to its motion
•

•

Movement away stretches the wavelength
• Longer wavelength
• Light appears redder
Movement toward “squeezes” the wavelength
• Shorter wavelength
• Light shifted toward the blue

24.4 Red shifts (continued)
 Doppler
•

effect

Amount of the Doppler shift indicates the
rate of movement
•
•

Large Doppler shift indicates a high velocity
Small Doppler shift indicates a lower velocity

 Expanding
•

universe

Most galaxies exhibit a red Doppler shift
•

Moving away

Raisin bread analogy of an
expanding universe

Figure 24.24

24.4 Red shifts (continued)
 Expanding
•

universe

Most galaxies exhibit a red Doppler shift
•

•
•
•

Far galaxies
• Exhibit the greatest shift
• Greater velocity
Discovered in 1929 by Edwin Hubble
Hubble's Law – the recessional speed of
galaxies is proportional to their distance
Accounts for red shifts

24.4 Big Bang theory
 Accounts

for galaxies moving away

from us
 Universe was once confined to a "ball"
that was
•
•

•

Supermassive
Dense
Hot

24.4 Big Bang theory (continued)
 Big

Bang marks the inception of the
universe
•
•

Occurred about 15 billion years ago
All matter and space was created

 Matter

is moving outward
 Fate of the universe
•

Two possibilities
•
•

Universe will last forever
Outward expansion sill stop and gravitational;
contraction will follow

24.4 Big Bang theory (continued)
 Fate
•

of the universe

Final fate depends on the average density
of the universe
•
•

If the density is more than the critical density,
then the universe would contract
Current estimates point to less then the critical
density and predict an ever-expanding, or
open, universe

Chapter 24Test Guidance
You will be responsible on the test for answering 3 of the following 6
questions.
1.

2.

3.
4.
5.
6.

What causes the difference between a star’s apparent
magnitude and it absolute magnitude.
List and explain the three factors that control the apparent
brightness of a star as seen from Earth.
Describe how binary stars are used to determine stellar mass.
List and describe the four basic types of galaxies.
What is Hubble’s Law, please explain in detail.
Briefly describe the Big Bang Theory (not the TV show).

End of Chapter 24


Slide 44

Lecture Outlines
PowerPoint

Chapter 24
Earth Science 11e
Tarbuck/Lutgens
Modified for educational
purposes only
By S. Koziol 12-8-2010

© 2006 Pearson Prentice Hall

Earth Science, 11e
Beyond Our
Solar System
Chapter 24

24.1 Properties of stars
 Distance
•
•

Measuring a star's distance can be very
difficult
Stellar parallax
•
•
•

•
•

Used for measuring distance to a star
Apparent shift in a star's position due to the
orbital motion of Earth
Measured as an angle
Near stars have the largest parallax
Largest parallax is less than one second of arc

24. 1 Properties of stars
(continued)

 Distance
•
•

Distances to the stars are very large
Units of measurement
•
•

•

Kilometers or astronomical units are too
cumbersome to use
Light-year is used most often
• Distance that light travels in 1 year
• One light-year is 9.5 trillion km (5.8 trillion
miles)

Other methods for measuring distance are
also used

24. 1 Properties of stars
(continued)

 Stellar
•

Controlled by three factors
•

•
•

•

brightness

Size
Temperature
Distance

Magnitude
•

Measure of a star's brightness

24.1 Properties of stars
(continued)

 Stellar
•

brightness

Magnitude
•

Two types of measurement
• Apparent magnitude
• Brightness when a star is viewed from
Earth
• Decreases with distance
• Numbers are used to designate
magnitudes - dim stars have large
numbers and negative numbers are also
used

24.1 Properties of stars
(continued)

 Stellar
•

brightness

Magnitude
•

Two types of measurement
• Absolute magnitude
• "True" or intrinsic brightness of a star
• Brightness at a standard distance of
32.6 light-years
• Most stars' absolute magnitudes are
between -5 and +15

24.1 Properties of stars
(continued)

 Color
•

Hot star
•

•
•

•

and temperature

Temperature above 30,000 K
Emits short-wavelength light
Appears blue

Cool star
•
•
•

Temperature less than 3000 K
Emits longer-wavelength light
Appears red

24.1 Properties of stars
(continued)

 Color
•

and temperature

Between 5000 and 6000 K
•
•

Stars appear yellow
e.g., Sun

 Binary
•

stars and stellar mass

Binary stars
•

Two stars orbiting one another
• Stars are held together by mutual
gravitation
• Both orbit around a common center of mass

24.1 Properties of stars (continued)
 Binary
•

Binary stars
•

•
•

•

stars and stellar mass

Visual binaries are resolved telescopically
More than 50% of the stars in the universe are
binary stars
Used to determine stellar mass

Stellar mass
•

Determined using binary stars – the center of
mass is closest to the most massive star

Binary stars
orbit each
other around
their common
center of
mass
Figure 24.4

24.1 Properties of stars (continued)
 Binary
•

stars and stellar mass

Stellar mass
•

Mass of most stars is between one-tenth and
fifty times the mass of the Sun

24.1 Hertzsprung-Russell
diagram
 Shows
•
•

the relation between stellar

Brightness (absolute magnitude) and
Temperature

 Diagram

is made by plotting (graphing)
each star's
•
•

Luminosity (brightness) and
Temperature

24.1 Hertzsprung-Russell
diagram (continued)
 Parts
•

Main-sequence stars
•

•
•

•

of an H-R diagram

90% of all stars
Band through the center of the H-R diagram
Sun is in the main-sequence

Giants (or red giants)
•
•
•

Very luminous
Large
Upper-right on the H-R diagram

24.1 Hertzsprung-Russell
diagram (continued)
 Parts
•

Giants (or red giants)
•

•

•

of an H-R diagram

Very large giants are called supergiants
Only a few percent of all stars

White dwarfs
•
•

•
•
•

Fainter than main-sequence stars
Small (approximate the size of Earth)
Lower-central area on the H-R diagram
Not all are white in color
Perhaps 10% of all stars

Idealized HertzsprungRussell diagram

Figure 24.5

Quiz Break

24.2 Variable stars
 Stars

that fluctuate in brightness
 Types of variable stars
•

Pulsating variables
•
•

•

Fluctuate regularly in brightness
Expand and contract in size

Eruptive variables
•
•
•

Explosive event
Sudden brightening
Called a nova

24.2 Interstellar matter
 Between

the stars is "the vacuum of

space"
 Nebula
•
•

Cloud of dust and gases
Two major types of nebulae
•

Bright nebula
• Glows if it close to a very hot star
• Two types of bright nebulae
• Emission nebula
• Reflection nebula

The Orion Nebula is a wellknown emission nebula

Figure 24.8

A faint blue reflection nebula in
the Pleiades star cluster

Figure 24.9

24.2 Interstellar matter (continued)
 Nebula
•

Two major types of nebulae
•

Dark nebula
• Not close to any bright star
• Appear dark
• Contains the material that forms stars and
planets

24.2 Stellar evolution
 Stars

exist because of gravity
 Two opposing forces in a star are
•
•

Gravity – contracts
Thermal nuclear energy – expands

 Stages
•

Birth
•

•
•
•
•

In dark, cool, interstellar clouds
Gravity contracts the cloud
Temperature rises
Radiates long-wavelength (red) light
Becomes a protostar

24.2 Stellar evolution (continued)
 Stages
•

Protostar
•
•
•

•
•
•
•

Gravitational contraction of gaseous cloud
continues
Core reaches 10 million K
Hydrogen nuclei fuse
• Become helium nuclei
• Process is called hydrogen burning
Energy is released
Outward pressure increases
Outward pressure balanced by gravity pulling in
Star becomes a stable main-sequence star

24.2 Stellar evolution (continued)
 Stages
•

Main-sequence stage
•

Stars age at different rates
• Massive stars use fuel faster and exist for
only a few million years
• Small stars use fuel slowly and exist for
perhaps hundreds of billions of years

•

90% of a star's life is in the main-sequence

24.2 Stellar evolution (continued)
 Stages
•

Red giant stage
•
•

•
•
•

Hydrogen burning migrates outward
Star's outer envelope expands
• Surface cools
• Surface becomes red
Core is collapsing as helium is converted to
carbon
Eventually all nuclear fuel is used
Gravity squeezes the star

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Low-mass star
• 0.5 solar mass
• Red giant collapses
• Becomes a white dwarf

24.2 Evolutionary stages of
low mass stars

Figure 24.12 A

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Medium-mass star
• Between 0.5 and 3 solar masses
• Red giant collapses
• Planetary nebula forms
• Becomes a white dwarf

24.2 Evolutionary stages of
medium mass stars

Figure 24.12 B

H-R diagram showing
stellar evolution

Figure 24.11

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Massive star
• Over 3 solar masses
• Short life span
• Terminates in a brilliant explosion called
a supernova
• Interior condenses
• May produce a hot, dense object that is
either a neutron star or a black hole

24.2 Evolutionary stages of
massive stars

Figure 24.12 C

24.2 Stellar remnants
 White
•
•

Small (some no larger than Earth)
Dense
•
•
•

•
•

dwarf

Can be more massive than the Sun
Spoonful weighs several tons
Atoms take up less space
• Electrons displaced inward
• Called degenerate matter

Hot surface
Cools to become a black dwarf

24.2 Stellar remnants (continued)
 Neutron
•

Forms from a more massive star
•
•

•
•

star

Star has more gravity
Squeezes itself smaller

Remnant of a supernova
Gravitational force collapses atoms
•
•

Electrons combine with protons to produce
neutrons
Small size

24.2 Stellar remnants (continued)
 Neutron
•

Pea size sample
•
•

•
•

star

Weighs 100 million tons
Same density as an atomic nucleus

Strong magnetic field
First one discovered in early 1970s
•
•

Pulsar (pulsating radio source)
Found in the Crab nebula (remnant of an A.D.
1054 supernova)

Crab Nebula in the
constellation Taurus

Figure 24.14

24.2 Stellar remnants (continued)
 Black
•
•

•

More dense than a neutron star
Intense surface gravity lets no light escape
As matter is pulled into it
•
•

•

hole

Becomes very hot
Emits x-rays

Likely candidate is Cygnus X-1, a strong xray source

Quiz Break

24.3 Galaxies
 Milky
•

Way galaxy

Structure
•
•

•
•

Determined by using radio telescopes
Large spiral galaxy
• About 100,000 light-years wide
• Thickness at the galactic nucleus is about
10,000 light-years
Three spiral arms of stars
Sun is 30,000 light-years from the center

Face-on view of the
Milk Way Galaxy

Figure 24.18 A

Edge-on view of the
Milk Way Galaxy

Figure 24.18 B

24.3 Galaxies (continued)
 Milky
•

Rotation
•
•
•

•

Way galaxy

Around the galactic nucleus
Outermost stars move the slowest
Sun rotates around the galactic nucleus once
about every 200 million years

Halo surrounds the galactic disk
•
•
•

Spherical
Very tenuous gas
Numerous globular clusters

24.3 Galaxies (continued)
 Other
•
•

galaxies

Existence was first proposed in mid-1700s
by Immanuel Kant
Four basic types of galaxies
•

Spiral galaxy
• Arms extending from nucleus
• About 30% of all galaxies
• Large diameter of 20,000 to 125,000 light
years
• Contains both young and old stars
• e.g., Milky Way

Great Galaxy, a spiral galaxy, in
the constellation Andromeda

Figure 24.20

24.3 Galaxies (continued)
 Other
•

galaxies

Four basic types of galaxies
•

•

Barred spiral galaxy
• Stars arranged in the shape of a bar
• Generally quite large
• About 10% of all galaxies
Elliptical galaxy
• Ellipsoidal shape
• About 60% of all galaxies
• Most are smaller than spiral galaxies;
however, they are also the largest known
galaxies

A barred spiral galaxy

Figure 24.22

24.3 Galaxies (continued)
 Other
•

galaxies

Four basic types of galaxies
•

Irregular galaxy
• Lacks symmetry
• About 10% of all galaxies
• Contains mostly young stars
• e.g., Magellanic Clouds

24.3 Galaxies (continued)
 Galactic
•
•
•

Group of galaxies
Some contain thousands of galaxies
Local Group
•
•

•

cluster

Our own group of galaxies
Contains at least 28 galaxies

Supercluster
•
•

Huge swarm of galaxies
May be the largest entity in the universe

Quiz Break

24.4 Red shifts
 Doppler
•

effect

Change in the wavelength of light emitted
by an object due to its motion
•

•

Movement away stretches the wavelength
• Longer wavelength
• Light appears redder
Movement toward “squeezes” the wavelength
• Shorter wavelength
• Light shifted toward the blue

24.4 Red shifts (continued)
 Doppler
•

effect

Amount of the Doppler shift indicates the
rate of movement
•
•

Large Doppler shift indicates a high velocity
Small Doppler shift indicates a lower velocity

 Expanding
•

universe

Most galaxies exhibit a red Doppler shift
•

Moving away

Raisin bread analogy of an
expanding universe

Figure 24.24

24.4 Red shifts (continued)
 Expanding
•

universe

Most galaxies exhibit a red Doppler shift
•

•
•
•

Far galaxies
• Exhibit the greatest shift
• Greater velocity
Discovered in 1929 by Edwin Hubble
Hubble's Law – the recessional speed of
galaxies is proportional to their distance
Accounts for red shifts

24.4 Big Bang theory
 Accounts

for galaxies moving away

from us
 Universe was once confined to a "ball"
that was
•
•

•

Supermassive
Dense
Hot

24.4 Big Bang theory (continued)
 Big

Bang marks the inception of the
universe
•
•

Occurred about 15 billion years ago
All matter and space was created

 Matter

is moving outward
 Fate of the universe
•

Two possibilities
•
•

Universe will last forever
Outward expansion sill stop and gravitational;
contraction will follow

24.4 Big Bang theory (continued)
 Fate
•

of the universe

Final fate depends on the average density
of the universe
•
•

If the density is more than the critical density,
then the universe would contract
Current estimates point to less then the critical
density and predict an ever-expanding, or
open, universe

Chapter 24Test Guidance
You will be responsible on the test for answering 3 of the following 6
questions.
1.

2.

3.
4.
5.
6.

What causes the difference between a star’s apparent
magnitude and it absolute magnitude.
List and explain the three factors that control the apparent
brightness of a star as seen from Earth.
Describe how binary stars are used to determine stellar mass.
List and describe the four basic types of galaxies.
What is Hubble’s Law, please explain in detail.
Briefly describe the Big Bang Theory (not the TV show).

End of Chapter 24


Slide 45

Lecture Outlines
PowerPoint

Chapter 24
Earth Science 11e
Tarbuck/Lutgens
Modified for educational
purposes only
By S. Koziol 12-8-2010

© 2006 Pearson Prentice Hall

Earth Science, 11e
Beyond Our
Solar System
Chapter 24

24.1 Properties of stars
 Distance
•
•

Measuring a star's distance can be very
difficult
Stellar parallax
•
•
•

•
•

Used for measuring distance to a star
Apparent shift in a star's position due to the
orbital motion of Earth
Measured as an angle
Near stars have the largest parallax
Largest parallax is less than one second of arc

24. 1 Properties of stars
(continued)

 Distance
•
•

Distances to the stars are very large
Units of measurement
•
•

•

Kilometers or astronomical units are too
cumbersome to use
Light-year is used most often
• Distance that light travels in 1 year
• One light-year is 9.5 trillion km (5.8 trillion
miles)

Other methods for measuring distance are
also used

24. 1 Properties of stars
(continued)

 Stellar
•

Controlled by three factors
•

•
•

•

brightness

Size
Temperature
Distance

Magnitude
•

Measure of a star's brightness

24.1 Properties of stars
(continued)

 Stellar
•

brightness

Magnitude
•

Two types of measurement
• Apparent magnitude
• Brightness when a star is viewed from
Earth
• Decreases with distance
• Numbers are used to designate
magnitudes - dim stars have large
numbers and negative numbers are also
used

24.1 Properties of stars
(continued)

 Stellar
•

brightness

Magnitude
•

Two types of measurement
• Absolute magnitude
• "True" or intrinsic brightness of a star
• Brightness at a standard distance of
32.6 light-years
• Most stars' absolute magnitudes are
between -5 and +15

24.1 Properties of stars
(continued)

 Color
•

Hot star
•

•
•

•

and temperature

Temperature above 30,000 K
Emits short-wavelength light
Appears blue

Cool star
•
•
•

Temperature less than 3000 K
Emits longer-wavelength light
Appears red

24.1 Properties of stars
(continued)

 Color
•

and temperature

Between 5000 and 6000 K
•
•

Stars appear yellow
e.g., Sun

 Binary
•

stars and stellar mass

Binary stars
•

Two stars orbiting one another
• Stars are held together by mutual
gravitation
• Both orbit around a common center of mass

24.1 Properties of stars (continued)
 Binary
•

Binary stars
•

•
•

•

stars and stellar mass

Visual binaries are resolved telescopically
More than 50% of the stars in the universe are
binary stars
Used to determine stellar mass

Stellar mass
•

Determined using binary stars – the center of
mass is closest to the most massive star

Binary stars
orbit each
other around
their common
center of
mass
Figure 24.4

24.1 Properties of stars (continued)
 Binary
•

stars and stellar mass

Stellar mass
•

Mass of most stars is between one-tenth and
fifty times the mass of the Sun

24.1 Hertzsprung-Russell
diagram
 Shows
•
•

the relation between stellar

Brightness (absolute magnitude) and
Temperature

 Diagram

is made by plotting (graphing)
each star's
•
•

Luminosity (brightness) and
Temperature

24.1 Hertzsprung-Russell
diagram (continued)
 Parts
•

Main-sequence stars
•

•
•

•

of an H-R diagram

90% of all stars
Band through the center of the H-R diagram
Sun is in the main-sequence

Giants (or red giants)
•
•
•

Very luminous
Large
Upper-right on the H-R diagram

24.1 Hertzsprung-Russell
diagram (continued)
 Parts
•

Giants (or red giants)
•

•

•

of an H-R diagram

Very large giants are called supergiants
Only a few percent of all stars

White dwarfs
•
•

•
•
•

Fainter than main-sequence stars
Small (approximate the size of Earth)
Lower-central area on the H-R diagram
Not all are white in color
Perhaps 10% of all stars

Idealized HertzsprungRussell diagram

Figure 24.5

Quiz Break

24.2 Variable stars
 Stars

that fluctuate in brightness
 Types of variable stars
•

Pulsating variables
•
•

•

Fluctuate regularly in brightness
Expand and contract in size

Eruptive variables
•
•
•

Explosive event
Sudden brightening
Called a nova

24.2 Interstellar matter
 Between

the stars is "the vacuum of

space"
 Nebula
•
•

Cloud of dust and gases
Two major types of nebulae
•

Bright nebula
• Glows if it close to a very hot star
• Two types of bright nebulae
• Emission nebula
• Reflection nebula

The Orion Nebula is a wellknown emission nebula

Figure 24.8

A faint blue reflection nebula in
the Pleiades star cluster

Figure 24.9

24.2 Interstellar matter (continued)
 Nebula
•

Two major types of nebulae
•

Dark nebula
• Not close to any bright star
• Appear dark
• Contains the material that forms stars and
planets

24.2 Stellar evolution
 Stars

exist because of gravity
 Two opposing forces in a star are
•
•

Gravity – contracts
Thermal nuclear energy – expands

 Stages
•

Birth
•

•
•
•
•

In dark, cool, interstellar clouds
Gravity contracts the cloud
Temperature rises
Radiates long-wavelength (red) light
Becomes a protostar

24.2 Stellar evolution (continued)
 Stages
•

Protostar
•
•
•

•
•
•
•

Gravitational contraction of gaseous cloud
continues
Core reaches 10 million K
Hydrogen nuclei fuse
• Become helium nuclei
• Process is called hydrogen burning
Energy is released
Outward pressure increases
Outward pressure balanced by gravity pulling in
Star becomes a stable main-sequence star

24.2 Stellar evolution (continued)
 Stages
•

Main-sequence stage
•

Stars age at different rates
• Massive stars use fuel faster and exist for
only a few million years
• Small stars use fuel slowly and exist for
perhaps hundreds of billions of years

•

90% of a star's life is in the main-sequence

24.2 Stellar evolution (continued)
 Stages
•

Red giant stage
•
•

•
•
•

Hydrogen burning migrates outward
Star's outer envelope expands
• Surface cools
• Surface becomes red
Core is collapsing as helium is converted to
carbon
Eventually all nuclear fuel is used
Gravity squeezes the star

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Low-mass star
• 0.5 solar mass
• Red giant collapses
• Becomes a white dwarf

24.2 Evolutionary stages of
low mass stars

Figure 24.12 A

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Medium-mass star
• Between 0.5 and 3 solar masses
• Red giant collapses
• Planetary nebula forms
• Becomes a white dwarf

24.2 Evolutionary stages of
medium mass stars

Figure 24.12 B

H-R diagram showing
stellar evolution

Figure 24.11

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Massive star
• Over 3 solar masses
• Short life span
• Terminates in a brilliant explosion called
a supernova
• Interior condenses
• May produce a hot, dense object that is
either a neutron star or a black hole

24.2 Evolutionary stages of
massive stars

Figure 24.12 C

24.2 Stellar remnants
 White
•
•

Small (some no larger than Earth)
Dense
•
•
•

•
•

dwarf

Can be more massive than the Sun
Spoonful weighs several tons
Atoms take up less space
• Electrons displaced inward
• Called degenerate matter

Hot surface
Cools to become a black dwarf

24.2 Stellar remnants (continued)
 Neutron
•

Forms from a more massive star
•
•

•
•

star

Star has more gravity
Squeezes itself smaller

Remnant of a supernova
Gravitational force collapses atoms
•
•

Electrons combine with protons to produce
neutrons
Small size

24.2 Stellar remnants (continued)
 Neutron
•

Pea size sample
•
•

•
•

star

Weighs 100 million tons
Same density as an atomic nucleus

Strong magnetic field
First one discovered in early 1970s
•
•

Pulsar (pulsating radio source)
Found in the Crab nebula (remnant of an A.D.
1054 supernova)

Crab Nebula in the
constellation Taurus

Figure 24.14

24.2 Stellar remnants (continued)
 Black
•
•

•

More dense than a neutron star
Intense surface gravity lets no light escape
As matter is pulled into it
•
•

•

hole

Becomes very hot
Emits x-rays

Likely candidate is Cygnus X-1, a strong xray source

Quiz Break

24.3 Galaxies
 Milky
•

Way galaxy

Structure
•
•

•
•

Determined by using radio telescopes
Large spiral galaxy
• About 100,000 light-years wide
• Thickness at the galactic nucleus is about
10,000 light-years
Three spiral arms of stars
Sun is 30,000 light-years from the center

Face-on view of the
Milk Way Galaxy

Figure 24.18 A

Edge-on view of the
Milk Way Galaxy

Figure 24.18 B

24.3 Galaxies (continued)
 Milky
•

Rotation
•
•
•

•

Way galaxy

Around the galactic nucleus
Outermost stars move the slowest
Sun rotates around the galactic nucleus once
about every 200 million years

Halo surrounds the galactic disk
•
•
•

Spherical
Very tenuous gas
Numerous globular clusters

24.3 Galaxies (continued)
 Other
•
•

galaxies

Existence was first proposed in mid-1700s
by Immanuel Kant
Four basic types of galaxies
•

Spiral galaxy
• Arms extending from nucleus
• About 30% of all galaxies
• Large diameter of 20,000 to 125,000 light
years
• Contains both young and old stars
• e.g., Milky Way

Great Galaxy, a spiral galaxy, in
the constellation Andromeda

Figure 24.20

24.3 Galaxies (continued)
 Other
•

galaxies

Four basic types of galaxies
•

•

Barred spiral galaxy
• Stars arranged in the shape of a bar
• Generally quite large
• About 10% of all galaxies
Elliptical galaxy
• Ellipsoidal shape
• About 60% of all galaxies
• Most are smaller than spiral galaxies;
however, they are also the largest known
galaxies

A barred spiral galaxy

Figure 24.22

24.3 Galaxies (continued)
 Other
•

galaxies

Four basic types of galaxies
•

Irregular galaxy
• Lacks symmetry
• About 10% of all galaxies
• Contains mostly young stars
• e.g., Magellanic Clouds

24.3 Galaxies (continued)
 Galactic
•
•
•

Group of galaxies
Some contain thousands of galaxies
Local Group
•
•

•

cluster

Our own group of galaxies
Contains at least 28 galaxies

Supercluster
•
•

Huge swarm of galaxies
May be the largest entity in the universe

Quiz Break

24.4 Red shifts
 Doppler
•

effect

Change in the wavelength of light emitted
by an object due to its motion
•

•

Movement away stretches the wavelength
• Longer wavelength
• Light appears redder
Movement toward “squeezes” the wavelength
• Shorter wavelength
• Light shifted toward the blue

24.4 Red shifts (continued)
 Doppler
•

effect

Amount of the Doppler shift indicates the
rate of movement
•
•

Large Doppler shift indicates a high velocity
Small Doppler shift indicates a lower velocity

 Expanding
•

universe

Most galaxies exhibit a red Doppler shift
•

Moving away

Raisin bread analogy of an
expanding universe

Figure 24.24

24.4 Red shifts (continued)
 Expanding
•

universe

Most galaxies exhibit a red Doppler shift
•

•
•
•

Far galaxies
• Exhibit the greatest shift
• Greater velocity
Discovered in 1929 by Edwin Hubble
Hubble's Law – the recessional speed of
galaxies is proportional to their distance
Accounts for red shifts

24.4 Big Bang theory
 Accounts

for galaxies moving away

from us
 Universe was once confined to a "ball"
that was
•
•

•

Supermassive
Dense
Hot

24.4 Big Bang theory (continued)
 Big

Bang marks the inception of the
universe
•
•

Occurred about 15 billion years ago
All matter and space was created

 Matter

is moving outward
 Fate of the universe
•

Two possibilities
•
•

Universe will last forever
Outward expansion sill stop and gravitational;
contraction will follow

24.4 Big Bang theory (continued)
 Fate
•

of the universe

Final fate depends on the average density
of the universe
•
•

If the density is more than the critical density,
then the universe would contract
Current estimates point to less then the critical
density and predict an ever-expanding, or
open, universe

Chapter 24Test Guidance
You will be responsible on the test for answering 3 of the following 6
questions.
1.

2.

3.
4.
5.
6.

What causes the difference between a star’s apparent
magnitude and it absolute magnitude.
List and explain the three factors that control the apparent
brightness of a star as seen from Earth.
Describe how binary stars are used to determine stellar mass.
List and describe the four basic types of galaxies.
What is Hubble’s Law, please explain in detail.
Briefly describe the Big Bang Theory (not the TV show).

End of Chapter 24


Slide 46

Lecture Outlines
PowerPoint

Chapter 24
Earth Science 11e
Tarbuck/Lutgens
Modified for educational
purposes only
By S. Koziol 12-8-2010

© 2006 Pearson Prentice Hall

Earth Science, 11e
Beyond Our
Solar System
Chapter 24

24.1 Properties of stars
 Distance
•
•

Measuring a star's distance can be very
difficult
Stellar parallax
•
•
•

•
•

Used for measuring distance to a star
Apparent shift in a star's position due to the
orbital motion of Earth
Measured as an angle
Near stars have the largest parallax
Largest parallax is less than one second of arc

24. 1 Properties of stars
(continued)

 Distance
•
•

Distances to the stars are very large
Units of measurement
•
•

•

Kilometers or astronomical units are too
cumbersome to use
Light-year is used most often
• Distance that light travels in 1 year
• One light-year is 9.5 trillion km (5.8 trillion
miles)

Other methods for measuring distance are
also used

24. 1 Properties of stars
(continued)

 Stellar
•

Controlled by three factors
•

•
•

•

brightness

Size
Temperature
Distance

Magnitude
•

Measure of a star's brightness

24.1 Properties of stars
(continued)

 Stellar
•

brightness

Magnitude
•

Two types of measurement
• Apparent magnitude
• Brightness when a star is viewed from
Earth
• Decreases with distance
• Numbers are used to designate
magnitudes - dim stars have large
numbers and negative numbers are also
used

24.1 Properties of stars
(continued)

 Stellar
•

brightness

Magnitude
•

Two types of measurement
• Absolute magnitude
• "True" or intrinsic brightness of a star
• Brightness at a standard distance of
32.6 light-years
• Most stars' absolute magnitudes are
between -5 and +15

24.1 Properties of stars
(continued)

 Color
•

Hot star
•

•
•

•

and temperature

Temperature above 30,000 K
Emits short-wavelength light
Appears blue

Cool star
•
•
•

Temperature less than 3000 K
Emits longer-wavelength light
Appears red

24.1 Properties of stars
(continued)

 Color
•

and temperature

Between 5000 and 6000 K
•
•

Stars appear yellow
e.g., Sun

 Binary
•

stars and stellar mass

Binary stars
•

Two stars orbiting one another
• Stars are held together by mutual
gravitation
• Both orbit around a common center of mass

24.1 Properties of stars (continued)
 Binary
•

Binary stars
•

•
•

•

stars and stellar mass

Visual binaries are resolved telescopically
More than 50% of the stars in the universe are
binary stars
Used to determine stellar mass

Stellar mass
•

Determined using binary stars – the center of
mass is closest to the most massive star

Binary stars
orbit each
other around
their common
center of
mass
Figure 24.4

24.1 Properties of stars (continued)
 Binary
•

stars and stellar mass

Stellar mass
•

Mass of most stars is between one-tenth and
fifty times the mass of the Sun

24.1 Hertzsprung-Russell
diagram
 Shows
•
•

the relation between stellar

Brightness (absolute magnitude) and
Temperature

 Diagram

is made by plotting (graphing)
each star's
•
•

Luminosity (brightness) and
Temperature

24.1 Hertzsprung-Russell
diagram (continued)
 Parts
•

Main-sequence stars
•

•
•

•

of an H-R diagram

90% of all stars
Band through the center of the H-R diagram
Sun is in the main-sequence

Giants (or red giants)
•
•
•

Very luminous
Large
Upper-right on the H-R diagram

24.1 Hertzsprung-Russell
diagram (continued)
 Parts
•

Giants (or red giants)
•

•

•

of an H-R diagram

Very large giants are called supergiants
Only a few percent of all stars

White dwarfs
•
•

•
•
•

Fainter than main-sequence stars
Small (approximate the size of Earth)
Lower-central area on the H-R diagram
Not all are white in color
Perhaps 10% of all stars

Idealized HertzsprungRussell diagram

Figure 24.5

Quiz Break

24.2 Variable stars
 Stars

that fluctuate in brightness
 Types of variable stars
•

Pulsating variables
•
•

•

Fluctuate regularly in brightness
Expand and contract in size

Eruptive variables
•
•
•

Explosive event
Sudden brightening
Called a nova

24.2 Interstellar matter
 Between

the stars is "the vacuum of

space"
 Nebula
•
•

Cloud of dust and gases
Two major types of nebulae
•

Bright nebula
• Glows if it close to a very hot star
• Two types of bright nebulae
• Emission nebula
• Reflection nebula

The Orion Nebula is a wellknown emission nebula

Figure 24.8

A faint blue reflection nebula in
the Pleiades star cluster

Figure 24.9

24.2 Interstellar matter (continued)
 Nebula
•

Two major types of nebulae
•

Dark nebula
• Not close to any bright star
• Appear dark
• Contains the material that forms stars and
planets

24.2 Stellar evolution
 Stars

exist because of gravity
 Two opposing forces in a star are
•
•

Gravity – contracts
Thermal nuclear energy – expands

 Stages
•

Birth
•

•
•
•
•

In dark, cool, interstellar clouds
Gravity contracts the cloud
Temperature rises
Radiates long-wavelength (red) light
Becomes a protostar

24.2 Stellar evolution (continued)
 Stages
•

Protostar
•
•
•

•
•
•
•

Gravitational contraction of gaseous cloud
continues
Core reaches 10 million K
Hydrogen nuclei fuse
• Become helium nuclei
• Process is called hydrogen burning
Energy is released
Outward pressure increases
Outward pressure balanced by gravity pulling in
Star becomes a stable main-sequence star

24.2 Stellar evolution (continued)
 Stages
•

Main-sequence stage
•

Stars age at different rates
• Massive stars use fuel faster and exist for
only a few million years
• Small stars use fuel slowly and exist for
perhaps hundreds of billions of years

•

90% of a star's life is in the main-sequence

24.2 Stellar evolution (continued)
 Stages
•

Red giant stage
•
•

•
•
•

Hydrogen burning migrates outward
Star's outer envelope expands
• Surface cools
• Surface becomes red
Core is collapsing as helium is converted to
carbon
Eventually all nuclear fuel is used
Gravity squeezes the star

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Low-mass star
• 0.5 solar mass
• Red giant collapses
• Becomes a white dwarf

24.2 Evolutionary stages of
low mass stars

Figure 24.12 A

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Medium-mass star
• Between 0.5 and 3 solar masses
• Red giant collapses
• Planetary nebula forms
• Becomes a white dwarf

24.2 Evolutionary stages of
medium mass stars

Figure 24.12 B

H-R diagram showing
stellar evolution

Figure 24.11

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Massive star
• Over 3 solar masses
• Short life span
• Terminates in a brilliant explosion called
a supernova
• Interior condenses
• May produce a hot, dense object that is
either a neutron star or a black hole

24.2 Evolutionary stages of
massive stars

Figure 24.12 C

24.2 Stellar remnants
 White
•
•

Small (some no larger than Earth)
Dense
•
•
•

•
•

dwarf

Can be more massive than the Sun
Spoonful weighs several tons
Atoms take up less space
• Electrons displaced inward
• Called degenerate matter

Hot surface
Cools to become a black dwarf

24.2 Stellar remnants (continued)
 Neutron
•

Forms from a more massive star
•
•

•
•

star

Star has more gravity
Squeezes itself smaller

Remnant of a supernova
Gravitational force collapses atoms
•
•

Electrons combine with protons to produce
neutrons
Small size

24.2 Stellar remnants (continued)
 Neutron
•

Pea size sample
•
•

•
•

star

Weighs 100 million tons
Same density as an atomic nucleus

Strong magnetic field
First one discovered in early 1970s
•
•

Pulsar (pulsating radio source)
Found in the Crab nebula (remnant of an A.D.
1054 supernova)

Crab Nebula in the
constellation Taurus

Figure 24.14

24.2 Stellar remnants (continued)
 Black
•
•

•

More dense than a neutron star
Intense surface gravity lets no light escape
As matter is pulled into it
•
•

•

hole

Becomes very hot
Emits x-rays

Likely candidate is Cygnus X-1, a strong xray source

Quiz Break

24.3 Galaxies
 Milky
•

Way galaxy

Structure
•
•

•
•

Determined by using radio telescopes
Large spiral galaxy
• About 100,000 light-years wide
• Thickness at the galactic nucleus is about
10,000 light-years
Three spiral arms of stars
Sun is 30,000 light-years from the center

Face-on view of the
Milk Way Galaxy

Figure 24.18 A

Edge-on view of the
Milk Way Galaxy

Figure 24.18 B

24.3 Galaxies (continued)
 Milky
•

Rotation
•
•
•

•

Way galaxy

Around the galactic nucleus
Outermost stars move the slowest
Sun rotates around the galactic nucleus once
about every 200 million years

Halo surrounds the galactic disk
•
•
•

Spherical
Very tenuous gas
Numerous globular clusters

24.3 Galaxies (continued)
 Other
•
•

galaxies

Existence was first proposed in mid-1700s
by Immanuel Kant
Four basic types of galaxies
•

Spiral galaxy
• Arms extending from nucleus
• About 30% of all galaxies
• Large diameter of 20,000 to 125,000 light
years
• Contains both young and old stars
• e.g., Milky Way

Great Galaxy, a spiral galaxy, in
the constellation Andromeda

Figure 24.20

24.3 Galaxies (continued)
 Other
•

galaxies

Four basic types of galaxies
•

•

Barred spiral galaxy
• Stars arranged in the shape of a bar
• Generally quite large
• About 10% of all galaxies
Elliptical galaxy
• Ellipsoidal shape
• About 60% of all galaxies
• Most are smaller than spiral galaxies;
however, they are also the largest known
galaxies

A barred spiral galaxy

Figure 24.22

24.3 Galaxies (continued)
 Other
•

galaxies

Four basic types of galaxies
•

Irregular galaxy
• Lacks symmetry
• About 10% of all galaxies
• Contains mostly young stars
• e.g., Magellanic Clouds

24.3 Galaxies (continued)
 Galactic
•
•
•

Group of galaxies
Some contain thousands of galaxies
Local Group
•
•

•

cluster

Our own group of galaxies
Contains at least 28 galaxies

Supercluster
•
•

Huge swarm of galaxies
May be the largest entity in the universe

Quiz Break

24.4 Red shifts
 Doppler
•

effect

Change in the wavelength of light emitted
by an object due to its motion
•

•

Movement away stretches the wavelength
• Longer wavelength
• Light appears redder
Movement toward “squeezes” the wavelength
• Shorter wavelength
• Light shifted toward the blue

24.4 Red shifts (continued)
 Doppler
•

effect

Amount of the Doppler shift indicates the
rate of movement
•
•

Large Doppler shift indicates a high velocity
Small Doppler shift indicates a lower velocity

 Expanding
•

universe

Most galaxies exhibit a red Doppler shift
•

Moving away

Raisin bread analogy of an
expanding universe

Figure 24.24

24.4 Red shifts (continued)
 Expanding
•

universe

Most galaxies exhibit a red Doppler shift
•

•
•
•

Far galaxies
• Exhibit the greatest shift
• Greater velocity
Discovered in 1929 by Edwin Hubble
Hubble's Law – the recessional speed of
galaxies is proportional to their distance
Accounts for red shifts

24.4 Big Bang theory
 Accounts

for galaxies moving away

from us
 Universe was once confined to a "ball"
that was
•
•

•

Supermassive
Dense
Hot

24.4 Big Bang theory (continued)
 Big

Bang marks the inception of the
universe
•
•

Occurred about 15 billion years ago
All matter and space was created

 Matter

is moving outward
 Fate of the universe
•

Two possibilities
•
•

Universe will last forever
Outward expansion sill stop and gravitational;
contraction will follow

24.4 Big Bang theory (continued)
 Fate
•

of the universe

Final fate depends on the average density
of the universe
•
•

If the density is more than the critical density,
then the universe would contract
Current estimates point to less then the critical
density and predict an ever-expanding, or
open, universe

Chapter 24Test Guidance
You will be responsible on the test for answering 3 of the following 6
questions.
1.

2.

3.
4.
5.
6.

What causes the difference between a star’s apparent
magnitude and it absolute magnitude.
List and explain the three factors that control the apparent
brightness of a star as seen from Earth.
Describe how binary stars are used to determine stellar mass.
List and describe the four basic types of galaxies.
What is Hubble’s Law, please explain in detail.
Briefly describe the Big Bang Theory (not the TV show).

End of Chapter 24


Slide 47

Lecture Outlines
PowerPoint

Chapter 24
Earth Science 11e
Tarbuck/Lutgens
Modified for educational
purposes only
By S. Koziol 12-8-2010

© 2006 Pearson Prentice Hall

Earth Science, 11e
Beyond Our
Solar System
Chapter 24

24.1 Properties of stars
 Distance
•
•

Measuring a star's distance can be very
difficult
Stellar parallax
•
•
•

•
•

Used for measuring distance to a star
Apparent shift in a star's position due to the
orbital motion of Earth
Measured as an angle
Near stars have the largest parallax
Largest parallax is less than one second of arc

24. 1 Properties of stars
(continued)

 Distance
•
•

Distances to the stars are very large
Units of measurement
•
•

•

Kilometers or astronomical units are too
cumbersome to use
Light-year is used most often
• Distance that light travels in 1 year
• One light-year is 9.5 trillion km (5.8 trillion
miles)

Other methods for measuring distance are
also used

24. 1 Properties of stars
(continued)

 Stellar
•

Controlled by three factors
•

•
•

•

brightness

Size
Temperature
Distance

Magnitude
•

Measure of a star's brightness

24.1 Properties of stars
(continued)

 Stellar
•

brightness

Magnitude
•

Two types of measurement
• Apparent magnitude
• Brightness when a star is viewed from
Earth
• Decreases with distance
• Numbers are used to designate
magnitudes - dim stars have large
numbers and negative numbers are also
used

24.1 Properties of stars
(continued)

 Stellar
•

brightness

Magnitude
•

Two types of measurement
• Absolute magnitude
• "True" or intrinsic brightness of a star
• Brightness at a standard distance of
32.6 light-years
• Most stars' absolute magnitudes are
between -5 and +15

24.1 Properties of stars
(continued)

 Color
•

Hot star
•

•
•

•

and temperature

Temperature above 30,000 K
Emits short-wavelength light
Appears blue

Cool star
•
•
•

Temperature less than 3000 K
Emits longer-wavelength light
Appears red

24.1 Properties of stars
(continued)

 Color
•

and temperature

Between 5000 and 6000 K
•
•

Stars appear yellow
e.g., Sun

 Binary
•

stars and stellar mass

Binary stars
•

Two stars orbiting one another
• Stars are held together by mutual
gravitation
• Both orbit around a common center of mass

24.1 Properties of stars (continued)
 Binary
•

Binary stars
•

•
•

•

stars and stellar mass

Visual binaries are resolved telescopically
More than 50% of the stars in the universe are
binary stars
Used to determine stellar mass

Stellar mass
•

Determined using binary stars – the center of
mass is closest to the most massive star

Binary stars
orbit each
other around
their common
center of
mass
Figure 24.4

24.1 Properties of stars (continued)
 Binary
•

stars and stellar mass

Stellar mass
•

Mass of most stars is between one-tenth and
fifty times the mass of the Sun

24.1 Hertzsprung-Russell
diagram
 Shows
•
•

the relation between stellar

Brightness (absolute magnitude) and
Temperature

 Diagram

is made by plotting (graphing)
each star's
•
•

Luminosity (brightness) and
Temperature

24.1 Hertzsprung-Russell
diagram (continued)
 Parts
•

Main-sequence stars
•

•
•

•

of an H-R diagram

90% of all stars
Band through the center of the H-R diagram
Sun is in the main-sequence

Giants (or red giants)
•
•
•

Very luminous
Large
Upper-right on the H-R diagram

24.1 Hertzsprung-Russell
diagram (continued)
 Parts
•

Giants (or red giants)
•

•

•

of an H-R diagram

Very large giants are called supergiants
Only a few percent of all stars

White dwarfs
•
•

•
•
•

Fainter than main-sequence stars
Small (approximate the size of Earth)
Lower-central area on the H-R diagram
Not all are white in color
Perhaps 10% of all stars

Idealized HertzsprungRussell diagram

Figure 24.5

Quiz Break

24.2 Variable stars
 Stars

that fluctuate in brightness
 Types of variable stars
•

Pulsating variables
•
•

•

Fluctuate regularly in brightness
Expand and contract in size

Eruptive variables
•
•
•

Explosive event
Sudden brightening
Called a nova

24.2 Interstellar matter
 Between

the stars is "the vacuum of

space"
 Nebula
•
•

Cloud of dust and gases
Two major types of nebulae
•

Bright nebula
• Glows if it close to a very hot star
• Two types of bright nebulae
• Emission nebula
• Reflection nebula

The Orion Nebula is a wellknown emission nebula

Figure 24.8

A faint blue reflection nebula in
the Pleiades star cluster

Figure 24.9

24.2 Interstellar matter (continued)
 Nebula
•

Two major types of nebulae
•

Dark nebula
• Not close to any bright star
• Appear dark
• Contains the material that forms stars and
planets

24.2 Stellar evolution
 Stars

exist because of gravity
 Two opposing forces in a star are
•
•

Gravity – contracts
Thermal nuclear energy – expands

 Stages
•

Birth
•

•
•
•
•

In dark, cool, interstellar clouds
Gravity contracts the cloud
Temperature rises
Radiates long-wavelength (red) light
Becomes a protostar

24.2 Stellar evolution (continued)
 Stages
•

Protostar
•
•
•

•
•
•
•

Gravitational contraction of gaseous cloud
continues
Core reaches 10 million K
Hydrogen nuclei fuse
• Become helium nuclei
• Process is called hydrogen burning
Energy is released
Outward pressure increases
Outward pressure balanced by gravity pulling in
Star becomes a stable main-sequence star

24.2 Stellar evolution (continued)
 Stages
•

Main-sequence stage
•

Stars age at different rates
• Massive stars use fuel faster and exist for
only a few million years
• Small stars use fuel slowly and exist for
perhaps hundreds of billions of years

•

90% of a star's life is in the main-sequence

24.2 Stellar evolution (continued)
 Stages
•

Red giant stage
•
•

•
•
•

Hydrogen burning migrates outward
Star's outer envelope expands
• Surface cools
• Surface becomes red
Core is collapsing as helium is converted to
carbon
Eventually all nuclear fuel is used
Gravity squeezes the star

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Low-mass star
• 0.5 solar mass
• Red giant collapses
• Becomes a white dwarf

24.2 Evolutionary stages of
low mass stars

Figure 24.12 A

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Medium-mass star
• Between 0.5 and 3 solar masses
• Red giant collapses
• Planetary nebula forms
• Becomes a white dwarf

24.2 Evolutionary stages of
medium mass stars

Figure 24.12 B

H-R diagram showing
stellar evolution

Figure 24.11

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Massive star
• Over 3 solar masses
• Short life span
• Terminates in a brilliant explosion called
a supernova
• Interior condenses
• May produce a hot, dense object that is
either a neutron star or a black hole

24.2 Evolutionary stages of
massive stars

Figure 24.12 C

24.2 Stellar remnants
 White
•
•

Small (some no larger than Earth)
Dense
•
•
•

•
•

dwarf

Can be more massive than the Sun
Spoonful weighs several tons
Atoms take up less space
• Electrons displaced inward
• Called degenerate matter

Hot surface
Cools to become a black dwarf

24.2 Stellar remnants (continued)
 Neutron
•

Forms from a more massive star
•
•

•
•

star

Star has more gravity
Squeezes itself smaller

Remnant of a supernova
Gravitational force collapses atoms
•
•

Electrons combine with protons to produce
neutrons
Small size

24.2 Stellar remnants (continued)
 Neutron
•

Pea size sample
•
•

•
•

star

Weighs 100 million tons
Same density as an atomic nucleus

Strong magnetic field
First one discovered in early 1970s
•
•

Pulsar (pulsating radio source)
Found in the Crab nebula (remnant of an A.D.
1054 supernova)

Crab Nebula in the
constellation Taurus

Figure 24.14

24.2 Stellar remnants (continued)
 Black
•
•

•

More dense than a neutron star
Intense surface gravity lets no light escape
As matter is pulled into it
•
•

•

hole

Becomes very hot
Emits x-rays

Likely candidate is Cygnus X-1, a strong xray source

Quiz Break

24.3 Galaxies
 Milky
•

Way galaxy

Structure
•
•

•
•

Determined by using radio telescopes
Large spiral galaxy
• About 100,000 light-years wide
• Thickness at the galactic nucleus is about
10,000 light-years
Three spiral arms of stars
Sun is 30,000 light-years from the center

Face-on view of the
Milk Way Galaxy

Figure 24.18 A

Edge-on view of the
Milk Way Galaxy

Figure 24.18 B

24.3 Galaxies (continued)
 Milky
•

Rotation
•
•
•

•

Way galaxy

Around the galactic nucleus
Outermost stars move the slowest
Sun rotates around the galactic nucleus once
about every 200 million years

Halo surrounds the galactic disk
•
•
•

Spherical
Very tenuous gas
Numerous globular clusters

24.3 Galaxies (continued)
 Other
•
•

galaxies

Existence was first proposed in mid-1700s
by Immanuel Kant
Four basic types of galaxies
•

Spiral galaxy
• Arms extending from nucleus
• About 30% of all galaxies
• Large diameter of 20,000 to 125,000 light
years
• Contains both young and old stars
• e.g., Milky Way

Great Galaxy, a spiral galaxy, in
the constellation Andromeda

Figure 24.20

24.3 Galaxies (continued)
 Other
•

galaxies

Four basic types of galaxies
•

•

Barred spiral galaxy
• Stars arranged in the shape of a bar
• Generally quite large
• About 10% of all galaxies
Elliptical galaxy
• Ellipsoidal shape
• About 60% of all galaxies
• Most are smaller than spiral galaxies;
however, they are also the largest known
galaxies

A barred spiral galaxy

Figure 24.22

24.3 Galaxies (continued)
 Other
•

galaxies

Four basic types of galaxies
•

Irregular galaxy
• Lacks symmetry
• About 10% of all galaxies
• Contains mostly young stars
• e.g., Magellanic Clouds

24.3 Galaxies (continued)
 Galactic
•
•
•

Group of galaxies
Some contain thousands of galaxies
Local Group
•
•

•

cluster

Our own group of galaxies
Contains at least 28 galaxies

Supercluster
•
•

Huge swarm of galaxies
May be the largest entity in the universe

Quiz Break

24.4 Red shifts
 Doppler
•

effect

Change in the wavelength of light emitted
by an object due to its motion
•

•

Movement away stretches the wavelength
• Longer wavelength
• Light appears redder
Movement toward “squeezes” the wavelength
• Shorter wavelength
• Light shifted toward the blue

24.4 Red shifts (continued)
 Doppler
•

effect

Amount of the Doppler shift indicates the
rate of movement
•
•

Large Doppler shift indicates a high velocity
Small Doppler shift indicates a lower velocity

 Expanding
•

universe

Most galaxies exhibit a red Doppler shift
•

Moving away

Raisin bread analogy of an
expanding universe

Figure 24.24

24.4 Red shifts (continued)
 Expanding
•

universe

Most galaxies exhibit a red Doppler shift
•

•
•
•

Far galaxies
• Exhibit the greatest shift
• Greater velocity
Discovered in 1929 by Edwin Hubble
Hubble's Law – the recessional speed of
galaxies is proportional to their distance
Accounts for red shifts

24.4 Big Bang theory
 Accounts

for galaxies moving away

from us
 Universe was once confined to a "ball"
that was
•
•

•

Supermassive
Dense
Hot

24.4 Big Bang theory (continued)
 Big

Bang marks the inception of the
universe
•
•

Occurred about 15 billion years ago
All matter and space was created

 Matter

is moving outward
 Fate of the universe
•

Two possibilities
•
•

Universe will last forever
Outward expansion sill stop and gravitational;
contraction will follow

24.4 Big Bang theory (continued)
 Fate
•

of the universe

Final fate depends on the average density
of the universe
•
•

If the density is more than the critical density,
then the universe would contract
Current estimates point to less then the critical
density and predict an ever-expanding, or
open, universe

Chapter 24Test Guidance
You will be responsible on the test for answering 3 of the following 6
questions.
1.

2.

3.
4.
5.
6.

What causes the difference between a star’s apparent
magnitude and it absolute magnitude.
List and explain the three factors that control the apparent
brightness of a star as seen from Earth.
Describe how binary stars are used to determine stellar mass.
List and describe the four basic types of galaxies.
What is Hubble’s Law, please explain in detail.
Briefly describe the Big Bang Theory (not the TV show).

End of Chapter 24


Slide 48

Lecture Outlines
PowerPoint

Chapter 24
Earth Science 11e
Tarbuck/Lutgens
Modified for educational
purposes only
By S. Koziol 12-8-2010

© 2006 Pearson Prentice Hall

Earth Science, 11e
Beyond Our
Solar System
Chapter 24

24.1 Properties of stars
 Distance
•
•

Measuring a star's distance can be very
difficult
Stellar parallax
•
•
•

•
•

Used for measuring distance to a star
Apparent shift in a star's position due to the
orbital motion of Earth
Measured as an angle
Near stars have the largest parallax
Largest parallax is less than one second of arc

24. 1 Properties of stars
(continued)

 Distance
•
•

Distances to the stars are very large
Units of measurement
•
•

•

Kilometers or astronomical units are too
cumbersome to use
Light-year is used most often
• Distance that light travels in 1 year
• One light-year is 9.5 trillion km (5.8 trillion
miles)

Other methods for measuring distance are
also used

24. 1 Properties of stars
(continued)

 Stellar
•

Controlled by three factors
•

•
•

•

brightness

Size
Temperature
Distance

Magnitude
•

Measure of a star's brightness

24.1 Properties of stars
(continued)

 Stellar
•

brightness

Magnitude
•

Two types of measurement
• Apparent magnitude
• Brightness when a star is viewed from
Earth
• Decreases with distance
• Numbers are used to designate
magnitudes - dim stars have large
numbers and negative numbers are also
used

24.1 Properties of stars
(continued)

 Stellar
•

brightness

Magnitude
•

Two types of measurement
• Absolute magnitude
• "True" or intrinsic brightness of a star
• Brightness at a standard distance of
32.6 light-years
• Most stars' absolute magnitudes are
between -5 and +15

24.1 Properties of stars
(continued)

 Color
•

Hot star
•

•
•

•

and temperature

Temperature above 30,000 K
Emits short-wavelength light
Appears blue

Cool star
•
•
•

Temperature less than 3000 K
Emits longer-wavelength light
Appears red

24.1 Properties of stars
(continued)

 Color
•

and temperature

Between 5000 and 6000 K
•
•

Stars appear yellow
e.g., Sun

 Binary
•

stars and stellar mass

Binary stars
•

Two stars orbiting one another
• Stars are held together by mutual
gravitation
• Both orbit around a common center of mass

24.1 Properties of stars (continued)
 Binary
•

Binary stars
•

•
•

•

stars and stellar mass

Visual binaries are resolved telescopically
More than 50% of the stars in the universe are
binary stars
Used to determine stellar mass

Stellar mass
•

Determined using binary stars – the center of
mass is closest to the most massive star

Binary stars
orbit each
other around
their common
center of
mass
Figure 24.4

24.1 Properties of stars (continued)
 Binary
•

stars and stellar mass

Stellar mass
•

Mass of most stars is between one-tenth and
fifty times the mass of the Sun

24.1 Hertzsprung-Russell
diagram
 Shows
•
•

the relation between stellar

Brightness (absolute magnitude) and
Temperature

 Diagram

is made by plotting (graphing)
each star's
•
•

Luminosity (brightness) and
Temperature

24.1 Hertzsprung-Russell
diagram (continued)
 Parts
•

Main-sequence stars
•

•
•

•

of an H-R diagram

90% of all stars
Band through the center of the H-R diagram
Sun is in the main-sequence

Giants (or red giants)
•
•
•

Very luminous
Large
Upper-right on the H-R diagram

24.1 Hertzsprung-Russell
diagram (continued)
 Parts
•

Giants (or red giants)
•

•

•

of an H-R diagram

Very large giants are called supergiants
Only a few percent of all stars

White dwarfs
•
•

•
•
•

Fainter than main-sequence stars
Small (approximate the size of Earth)
Lower-central area on the H-R diagram
Not all are white in color
Perhaps 10% of all stars

Idealized HertzsprungRussell diagram

Figure 24.5

Quiz Break

24.2 Variable stars
 Stars

that fluctuate in brightness
 Types of variable stars
•

Pulsating variables
•
•

•

Fluctuate regularly in brightness
Expand and contract in size

Eruptive variables
•
•
•

Explosive event
Sudden brightening
Called a nova

24.2 Interstellar matter
 Between

the stars is "the vacuum of

space"
 Nebula
•
•

Cloud of dust and gases
Two major types of nebulae
•

Bright nebula
• Glows if it close to a very hot star
• Two types of bright nebulae
• Emission nebula
• Reflection nebula

The Orion Nebula is a wellknown emission nebula

Figure 24.8

A faint blue reflection nebula in
the Pleiades star cluster

Figure 24.9

24.2 Interstellar matter (continued)
 Nebula
•

Two major types of nebulae
•

Dark nebula
• Not close to any bright star
• Appear dark
• Contains the material that forms stars and
planets

24.2 Stellar evolution
 Stars

exist because of gravity
 Two opposing forces in a star are
•
•

Gravity – contracts
Thermal nuclear energy – expands

 Stages
•

Birth
•

•
•
•
•

In dark, cool, interstellar clouds
Gravity contracts the cloud
Temperature rises
Radiates long-wavelength (red) light
Becomes a protostar

24.2 Stellar evolution (continued)
 Stages
•

Protostar
•
•
•

•
•
•
•

Gravitational contraction of gaseous cloud
continues
Core reaches 10 million K
Hydrogen nuclei fuse
• Become helium nuclei
• Process is called hydrogen burning
Energy is released
Outward pressure increases
Outward pressure balanced by gravity pulling in
Star becomes a stable main-sequence star

24.2 Stellar evolution (continued)
 Stages
•

Main-sequence stage
•

Stars age at different rates
• Massive stars use fuel faster and exist for
only a few million years
• Small stars use fuel slowly and exist for
perhaps hundreds of billions of years

•

90% of a star's life is in the main-sequence

24.2 Stellar evolution (continued)
 Stages
•

Red giant stage
•
•

•
•
•

Hydrogen burning migrates outward
Star's outer envelope expands
• Surface cools
• Surface becomes red
Core is collapsing as helium is converted to
carbon
Eventually all nuclear fuel is used
Gravity squeezes the star

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Low-mass star
• 0.5 solar mass
• Red giant collapses
• Becomes a white dwarf

24.2 Evolutionary stages of
low mass stars

Figure 24.12 A

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Medium-mass star
• Between 0.5 and 3 solar masses
• Red giant collapses
• Planetary nebula forms
• Becomes a white dwarf

24.2 Evolutionary stages of
medium mass stars

Figure 24.12 B

H-R diagram showing
stellar evolution

Figure 24.11

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Massive star
• Over 3 solar masses
• Short life span
• Terminates in a brilliant explosion called
a supernova
• Interior condenses
• May produce a hot, dense object that is
either a neutron star or a black hole

24.2 Evolutionary stages of
massive stars

Figure 24.12 C

24.2 Stellar remnants
 White
•
•

Small (some no larger than Earth)
Dense
•
•
•

•
•

dwarf

Can be more massive than the Sun
Spoonful weighs several tons
Atoms take up less space
• Electrons displaced inward
• Called degenerate matter

Hot surface
Cools to become a black dwarf

24.2 Stellar remnants (continued)
 Neutron
•

Forms from a more massive star
•
•

•
•

star

Star has more gravity
Squeezes itself smaller

Remnant of a supernova
Gravitational force collapses atoms
•
•

Electrons combine with protons to produce
neutrons
Small size

24.2 Stellar remnants (continued)
 Neutron
•

Pea size sample
•
•

•
•

star

Weighs 100 million tons
Same density as an atomic nucleus

Strong magnetic field
First one discovered in early 1970s
•
•

Pulsar (pulsating radio source)
Found in the Crab nebula (remnant of an A.D.
1054 supernova)

Crab Nebula in the
constellation Taurus

Figure 24.14

24.2 Stellar remnants (continued)
 Black
•
•

•

More dense than a neutron star
Intense surface gravity lets no light escape
As matter is pulled into it
•
•

•

hole

Becomes very hot
Emits x-rays

Likely candidate is Cygnus X-1, a strong xray source

Quiz Break

24.3 Galaxies
 Milky
•

Way galaxy

Structure
•
•

•
•

Determined by using radio telescopes
Large spiral galaxy
• About 100,000 light-years wide
• Thickness at the galactic nucleus is about
10,000 light-years
Three spiral arms of stars
Sun is 30,000 light-years from the center

Face-on view of the
Milk Way Galaxy

Figure 24.18 A

Edge-on view of the
Milk Way Galaxy

Figure 24.18 B

24.3 Galaxies (continued)
 Milky
•

Rotation
•
•
•

•

Way galaxy

Around the galactic nucleus
Outermost stars move the slowest
Sun rotates around the galactic nucleus once
about every 200 million years

Halo surrounds the galactic disk
•
•
•

Spherical
Very tenuous gas
Numerous globular clusters

24.3 Galaxies (continued)
 Other
•
•

galaxies

Existence was first proposed in mid-1700s
by Immanuel Kant
Four basic types of galaxies
•

Spiral galaxy
• Arms extending from nucleus
• About 30% of all galaxies
• Large diameter of 20,000 to 125,000 light
years
• Contains both young and old stars
• e.g., Milky Way

Great Galaxy, a spiral galaxy, in
the constellation Andromeda

Figure 24.20

24.3 Galaxies (continued)
 Other
•

galaxies

Four basic types of galaxies
•

•

Barred spiral galaxy
• Stars arranged in the shape of a bar
• Generally quite large
• About 10% of all galaxies
Elliptical galaxy
• Ellipsoidal shape
• About 60% of all galaxies
• Most are smaller than spiral galaxies;
however, they are also the largest known
galaxies

A barred spiral galaxy

Figure 24.22

24.3 Galaxies (continued)
 Other
•

galaxies

Four basic types of galaxies
•

Irregular galaxy
• Lacks symmetry
• About 10% of all galaxies
• Contains mostly young stars
• e.g., Magellanic Clouds

24.3 Galaxies (continued)
 Galactic
•
•
•

Group of galaxies
Some contain thousands of galaxies
Local Group
•
•

•

cluster

Our own group of galaxies
Contains at least 28 galaxies

Supercluster
•
•

Huge swarm of galaxies
May be the largest entity in the universe

Quiz Break

24.4 Red shifts
 Doppler
•

effect

Change in the wavelength of light emitted
by an object due to its motion
•

•

Movement away stretches the wavelength
• Longer wavelength
• Light appears redder
Movement toward “squeezes” the wavelength
• Shorter wavelength
• Light shifted toward the blue

24.4 Red shifts (continued)
 Doppler
•

effect

Amount of the Doppler shift indicates the
rate of movement
•
•

Large Doppler shift indicates a high velocity
Small Doppler shift indicates a lower velocity

 Expanding
•

universe

Most galaxies exhibit a red Doppler shift
•

Moving away

Raisin bread analogy of an
expanding universe

Figure 24.24

24.4 Red shifts (continued)
 Expanding
•

universe

Most galaxies exhibit a red Doppler shift
•

•
•
•

Far galaxies
• Exhibit the greatest shift
• Greater velocity
Discovered in 1929 by Edwin Hubble
Hubble's Law – the recessional speed of
galaxies is proportional to their distance
Accounts for red shifts

24.4 Big Bang theory
 Accounts

for galaxies moving away

from us
 Universe was once confined to a "ball"
that was
•
•

•

Supermassive
Dense
Hot

24.4 Big Bang theory (continued)
 Big

Bang marks the inception of the
universe
•
•

Occurred about 15 billion years ago
All matter and space was created

 Matter

is moving outward
 Fate of the universe
•

Two possibilities
•
•

Universe will last forever
Outward expansion sill stop and gravitational;
contraction will follow

24.4 Big Bang theory (continued)
 Fate
•

of the universe

Final fate depends on the average density
of the universe
•
•

If the density is more than the critical density,
then the universe would contract
Current estimates point to less then the critical
density and predict an ever-expanding, or
open, universe

Chapter 24Test Guidance
You will be responsible on the test for answering 3 of the following 6
questions.
1.

2.

3.
4.
5.
6.

What causes the difference between a star’s apparent
magnitude and it absolute magnitude.
List and explain the three factors that control the apparent
brightness of a star as seen from Earth.
Describe how binary stars are used to determine stellar mass.
List and describe the four basic types of galaxies.
What is Hubble’s Law, please explain in detail.
Briefly describe the Big Bang Theory (not the TV show).

End of Chapter 24


Slide 49

Lecture Outlines
PowerPoint

Chapter 24
Earth Science 11e
Tarbuck/Lutgens
Modified for educational
purposes only
By S. Koziol 12-8-2010

© 2006 Pearson Prentice Hall

Earth Science, 11e
Beyond Our
Solar System
Chapter 24

24.1 Properties of stars
 Distance
•
•

Measuring a star's distance can be very
difficult
Stellar parallax
•
•
•

•
•

Used for measuring distance to a star
Apparent shift in a star's position due to the
orbital motion of Earth
Measured as an angle
Near stars have the largest parallax
Largest parallax is less than one second of arc

24. 1 Properties of stars
(continued)

 Distance
•
•

Distances to the stars are very large
Units of measurement
•
•

•

Kilometers or astronomical units are too
cumbersome to use
Light-year is used most often
• Distance that light travels in 1 year
• One light-year is 9.5 trillion km (5.8 trillion
miles)

Other methods for measuring distance are
also used

24. 1 Properties of stars
(continued)

 Stellar
•

Controlled by three factors
•

•
•

•

brightness

Size
Temperature
Distance

Magnitude
•

Measure of a star's brightness

24.1 Properties of stars
(continued)

 Stellar
•

brightness

Magnitude
•

Two types of measurement
• Apparent magnitude
• Brightness when a star is viewed from
Earth
• Decreases with distance
• Numbers are used to designate
magnitudes - dim stars have large
numbers and negative numbers are also
used

24.1 Properties of stars
(continued)

 Stellar
•

brightness

Magnitude
•

Two types of measurement
• Absolute magnitude
• "True" or intrinsic brightness of a star
• Brightness at a standard distance of
32.6 light-years
• Most stars' absolute magnitudes are
between -5 and +15

24.1 Properties of stars
(continued)

 Color
•

Hot star
•

•
•

•

and temperature

Temperature above 30,000 K
Emits short-wavelength light
Appears blue

Cool star
•
•
•

Temperature less than 3000 K
Emits longer-wavelength light
Appears red

24.1 Properties of stars
(continued)

 Color
•

and temperature

Between 5000 and 6000 K
•
•

Stars appear yellow
e.g., Sun

 Binary
•

stars and stellar mass

Binary stars
•

Two stars orbiting one another
• Stars are held together by mutual
gravitation
• Both orbit around a common center of mass

24.1 Properties of stars (continued)
 Binary
•

Binary stars
•

•
•

•

stars and stellar mass

Visual binaries are resolved telescopically
More than 50% of the stars in the universe are
binary stars
Used to determine stellar mass

Stellar mass
•

Determined using binary stars – the center of
mass is closest to the most massive star

Binary stars
orbit each
other around
their common
center of
mass
Figure 24.4

24.1 Properties of stars (continued)
 Binary
•

stars and stellar mass

Stellar mass
•

Mass of most stars is between one-tenth and
fifty times the mass of the Sun

24.1 Hertzsprung-Russell
diagram
 Shows
•
•

the relation between stellar

Brightness (absolute magnitude) and
Temperature

 Diagram

is made by plotting (graphing)
each star's
•
•

Luminosity (brightness) and
Temperature

24.1 Hertzsprung-Russell
diagram (continued)
 Parts
•

Main-sequence stars
•

•
•

•

of an H-R diagram

90% of all stars
Band through the center of the H-R diagram
Sun is in the main-sequence

Giants (or red giants)
•
•
•

Very luminous
Large
Upper-right on the H-R diagram

24.1 Hertzsprung-Russell
diagram (continued)
 Parts
•

Giants (or red giants)
•

•

•

of an H-R diagram

Very large giants are called supergiants
Only a few percent of all stars

White dwarfs
•
•

•
•
•

Fainter than main-sequence stars
Small (approximate the size of Earth)
Lower-central area on the H-R diagram
Not all are white in color
Perhaps 10% of all stars

Idealized HertzsprungRussell diagram

Figure 24.5

Quiz Break

24.2 Variable stars
 Stars

that fluctuate in brightness
 Types of variable stars
•

Pulsating variables
•
•

•

Fluctuate regularly in brightness
Expand and contract in size

Eruptive variables
•
•
•

Explosive event
Sudden brightening
Called a nova

24.2 Interstellar matter
 Between

the stars is "the vacuum of

space"
 Nebula
•
•

Cloud of dust and gases
Two major types of nebulae
•

Bright nebula
• Glows if it close to a very hot star
• Two types of bright nebulae
• Emission nebula
• Reflection nebula

The Orion Nebula is a wellknown emission nebula

Figure 24.8

A faint blue reflection nebula in
the Pleiades star cluster

Figure 24.9

24.2 Interstellar matter (continued)
 Nebula
•

Two major types of nebulae
•

Dark nebula
• Not close to any bright star
• Appear dark
• Contains the material that forms stars and
planets

24.2 Stellar evolution
 Stars

exist because of gravity
 Two opposing forces in a star are
•
•

Gravity – contracts
Thermal nuclear energy – expands

 Stages
•

Birth
•

•
•
•
•

In dark, cool, interstellar clouds
Gravity contracts the cloud
Temperature rises
Radiates long-wavelength (red) light
Becomes a protostar

24.2 Stellar evolution (continued)
 Stages
•

Protostar
•
•
•

•
•
•
•

Gravitational contraction of gaseous cloud
continues
Core reaches 10 million K
Hydrogen nuclei fuse
• Become helium nuclei
• Process is called hydrogen burning
Energy is released
Outward pressure increases
Outward pressure balanced by gravity pulling in
Star becomes a stable main-sequence star

24.2 Stellar evolution (continued)
 Stages
•

Main-sequence stage
•

Stars age at different rates
• Massive stars use fuel faster and exist for
only a few million years
• Small stars use fuel slowly and exist for
perhaps hundreds of billions of years

•

90% of a star's life is in the main-sequence

24.2 Stellar evolution (continued)
 Stages
•

Red giant stage
•
•

•
•
•

Hydrogen burning migrates outward
Star's outer envelope expands
• Surface cools
• Surface becomes red
Core is collapsing as helium is converted to
carbon
Eventually all nuclear fuel is used
Gravity squeezes the star

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Low-mass star
• 0.5 solar mass
• Red giant collapses
• Becomes a white dwarf

24.2 Evolutionary stages of
low mass stars

Figure 24.12 A

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Medium-mass star
• Between 0.5 and 3 solar masses
• Red giant collapses
• Planetary nebula forms
• Becomes a white dwarf

24.2 Evolutionary stages of
medium mass stars

Figure 24.12 B

H-R diagram showing
stellar evolution

Figure 24.11

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Massive star
• Over 3 solar masses
• Short life span
• Terminates in a brilliant explosion called
a supernova
• Interior condenses
• May produce a hot, dense object that is
either a neutron star or a black hole

24.2 Evolutionary stages of
massive stars

Figure 24.12 C

24.2 Stellar remnants
 White
•
•

Small (some no larger than Earth)
Dense
•
•
•

•
•

dwarf

Can be more massive than the Sun
Spoonful weighs several tons
Atoms take up less space
• Electrons displaced inward
• Called degenerate matter

Hot surface
Cools to become a black dwarf

24.2 Stellar remnants (continued)
 Neutron
•

Forms from a more massive star
•
•

•
•

star

Star has more gravity
Squeezes itself smaller

Remnant of a supernova
Gravitational force collapses atoms
•
•

Electrons combine with protons to produce
neutrons
Small size

24.2 Stellar remnants (continued)
 Neutron
•

Pea size sample
•
•

•
•

star

Weighs 100 million tons
Same density as an atomic nucleus

Strong magnetic field
First one discovered in early 1970s
•
•

Pulsar (pulsating radio source)
Found in the Crab nebula (remnant of an A.D.
1054 supernova)

Crab Nebula in the
constellation Taurus

Figure 24.14

24.2 Stellar remnants (continued)
 Black
•
•

•

More dense than a neutron star
Intense surface gravity lets no light escape
As matter is pulled into it
•
•

•

hole

Becomes very hot
Emits x-rays

Likely candidate is Cygnus X-1, a strong xray source

Quiz Break

24.3 Galaxies
 Milky
•

Way galaxy

Structure
•
•

•
•

Determined by using radio telescopes
Large spiral galaxy
• About 100,000 light-years wide
• Thickness at the galactic nucleus is about
10,000 light-years
Three spiral arms of stars
Sun is 30,000 light-years from the center

Face-on view of the
Milk Way Galaxy

Figure 24.18 A

Edge-on view of the
Milk Way Galaxy

Figure 24.18 B

24.3 Galaxies (continued)
 Milky
•

Rotation
•
•
•

•

Way galaxy

Around the galactic nucleus
Outermost stars move the slowest
Sun rotates around the galactic nucleus once
about every 200 million years

Halo surrounds the galactic disk
•
•
•

Spherical
Very tenuous gas
Numerous globular clusters

24.3 Galaxies (continued)
 Other
•
•

galaxies

Existence was first proposed in mid-1700s
by Immanuel Kant
Four basic types of galaxies
•

Spiral galaxy
• Arms extending from nucleus
• About 30% of all galaxies
• Large diameter of 20,000 to 125,000 light
years
• Contains both young and old stars
• e.g., Milky Way

Great Galaxy, a spiral galaxy, in
the constellation Andromeda

Figure 24.20

24.3 Galaxies (continued)
 Other
•

galaxies

Four basic types of galaxies
•

•

Barred spiral galaxy
• Stars arranged in the shape of a bar
• Generally quite large
• About 10% of all galaxies
Elliptical galaxy
• Ellipsoidal shape
• About 60% of all galaxies
• Most are smaller than spiral galaxies;
however, they are also the largest known
galaxies

A barred spiral galaxy

Figure 24.22

24.3 Galaxies (continued)
 Other
•

galaxies

Four basic types of galaxies
•

Irregular galaxy
• Lacks symmetry
• About 10% of all galaxies
• Contains mostly young stars
• e.g., Magellanic Clouds

24.3 Galaxies (continued)
 Galactic
•
•
•

Group of galaxies
Some contain thousands of galaxies
Local Group
•
•

•

cluster

Our own group of galaxies
Contains at least 28 galaxies

Supercluster
•
•

Huge swarm of galaxies
May be the largest entity in the universe

Quiz Break

24.4 Red shifts
 Doppler
•

effect

Change in the wavelength of light emitted
by an object due to its motion
•

•

Movement away stretches the wavelength
• Longer wavelength
• Light appears redder
Movement toward “squeezes” the wavelength
• Shorter wavelength
• Light shifted toward the blue

24.4 Red shifts (continued)
 Doppler
•

effect

Amount of the Doppler shift indicates the
rate of movement
•
•

Large Doppler shift indicates a high velocity
Small Doppler shift indicates a lower velocity

 Expanding
•

universe

Most galaxies exhibit a red Doppler shift
•

Moving away

Raisin bread analogy of an
expanding universe

Figure 24.24

24.4 Red shifts (continued)
 Expanding
•

universe

Most galaxies exhibit a red Doppler shift
•

•
•
•

Far galaxies
• Exhibit the greatest shift
• Greater velocity
Discovered in 1929 by Edwin Hubble
Hubble's Law – the recessional speed of
galaxies is proportional to their distance
Accounts for red shifts

24.4 Big Bang theory
 Accounts

for galaxies moving away

from us
 Universe was once confined to a "ball"
that was
•
•

•

Supermassive
Dense
Hot

24.4 Big Bang theory (continued)
 Big

Bang marks the inception of the
universe
•
•

Occurred about 15 billion years ago
All matter and space was created

 Matter

is moving outward
 Fate of the universe
•

Two possibilities
•
•

Universe will last forever
Outward expansion sill stop and gravitational;
contraction will follow

24.4 Big Bang theory (continued)
 Fate
•

of the universe

Final fate depends on the average density
of the universe
•
•

If the density is more than the critical density,
then the universe would contract
Current estimates point to less then the critical
density and predict an ever-expanding, or
open, universe

Chapter 24Test Guidance
You will be responsible on the test for answering 3 of the following 6
questions.
1.

2.

3.
4.
5.
6.

What causes the difference between a star’s apparent
magnitude and it absolute magnitude.
List and explain the three factors that control the apparent
brightness of a star as seen from Earth.
Describe how binary stars are used to determine stellar mass.
List and describe the four basic types of galaxies.
What is Hubble’s Law, please explain in detail.
Briefly describe the Big Bang Theory (not the TV show).

End of Chapter 24


Slide 50

Lecture Outlines
PowerPoint

Chapter 24
Earth Science 11e
Tarbuck/Lutgens
Modified for educational
purposes only
By S. Koziol 12-8-2010

© 2006 Pearson Prentice Hall

Earth Science, 11e
Beyond Our
Solar System
Chapter 24

24.1 Properties of stars
 Distance
•
•

Measuring a star's distance can be very
difficult
Stellar parallax
•
•
•

•
•

Used for measuring distance to a star
Apparent shift in a star's position due to the
orbital motion of Earth
Measured as an angle
Near stars have the largest parallax
Largest parallax is less than one second of arc

24. 1 Properties of stars
(continued)

 Distance
•
•

Distances to the stars are very large
Units of measurement
•
•

•

Kilometers or astronomical units are too
cumbersome to use
Light-year is used most often
• Distance that light travels in 1 year
• One light-year is 9.5 trillion km (5.8 trillion
miles)

Other methods for measuring distance are
also used

24. 1 Properties of stars
(continued)

 Stellar
•

Controlled by three factors
•

•
•

•

brightness

Size
Temperature
Distance

Magnitude
•

Measure of a star's brightness

24.1 Properties of stars
(continued)

 Stellar
•

brightness

Magnitude
•

Two types of measurement
• Apparent magnitude
• Brightness when a star is viewed from
Earth
• Decreases with distance
• Numbers are used to designate
magnitudes - dim stars have large
numbers and negative numbers are also
used

24.1 Properties of stars
(continued)

 Stellar
•

brightness

Magnitude
•

Two types of measurement
• Absolute magnitude
• "True" or intrinsic brightness of a star
• Brightness at a standard distance of
32.6 light-years
• Most stars' absolute magnitudes are
between -5 and +15

24.1 Properties of stars
(continued)

 Color
•

Hot star
•

•
•

•

and temperature

Temperature above 30,000 K
Emits short-wavelength light
Appears blue

Cool star
•
•
•

Temperature less than 3000 K
Emits longer-wavelength light
Appears red

24.1 Properties of stars
(continued)

 Color
•

and temperature

Between 5000 and 6000 K
•
•

Stars appear yellow
e.g., Sun

 Binary
•

stars and stellar mass

Binary stars
•

Two stars orbiting one another
• Stars are held together by mutual
gravitation
• Both orbit around a common center of mass

24.1 Properties of stars (continued)
 Binary
•

Binary stars
•

•
•

•

stars and stellar mass

Visual binaries are resolved telescopically
More than 50% of the stars in the universe are
binary stars
Used to determine stellar mass

Stellar mass
•

Determined using binary stars – the center of
mass is closest to the most massive star

Binary stars
orbit each
other around
their common
center of
mass
Figure 24.4

24.1 Properties of stars (continued)
 Binary
•

stars and stellar mass

Stellar mass
•

Mass of most stars is between one-tenth and
fifty times the mass of the Sun

24.1 Hertzsprung-Russell
diagram
 Shows
•
•

the relation between stellar

Brightness (absolute magnitude) and
Temperature

 Diagram

is made by plotting (graphing)
each star's
•
•

Luminosity (brightness) and
Temperature

24.1 Hertzsprung-Russell
diagram (continued)
 Parts
•

Main-sequence stars
•

•
•

•

of an H-R diagram

90% of all stars
Band through the center of the H-R diagram
Sun is in the main-sequence

Giants (or red giants)
•
•
•

Very luminous
Large
Upper-right on the H-R diagram

24.1 Hertzsprung-Russell
diagram (continued)
 Parts
•

Giants (or red giants)
•

•

•

of an H-R diagram

Very large giants are called supergiants
Only a few percent of all stars

White dwarfs
•
•

•
•
•

Fainter than main-sequence stars
Small (approximate the size of Earth)
Lower-central area on the H-R diagram
Not all are white in color
Perhaps 10% of all stars

Idealized HertzsprungRussell diagram

Figure 24.5

Quiz Break

24.2 Variable stars
 Stars

that fluctuate in brightness
 Types of variable stars
•

Pulsating variables
•
•

•

Fluctuate regularly in brightness
Expand and contract in size

Eruptive variables
•
•
•

Explosive event
Sudden brightening
Called a nova

24.2 Interstellar matter
 Between

the stars is "the vacuum of

space"
 Nebula
•
•

Cloud of dust and gases
Two major types of nebulae
•

Bright nebula
• Glows if it close to a very hot star
• Two types of bright nebulae
• Emission nebula
• Reflection nebula

The Orion Nebula is a wellknown emission nebula

Figure 24.8

A faint blue reflection nebula in
the Pleiades star cluster

Figure 24.9

24.2 Interstellar matter (continued)
 Nebula
•

Two major types of nebulae
•

Dark nebula
• Not close to any bright star
• Appear dark
• Contains the material that forms stars and
planets

24.2 Stellar evolution
 Stars

exist because of gravity
 Two opposing forces in a star are
•
•

Gravity – contracts
Thermal nuclear energy – expands

 Stages
•

Birth
•

•
•
•
•

In dark, cool, interstellar clouds
Gravity contracts the cloud
Temperature rises
Radiates long-wavelength (red) light
Becomes a protostar

24.2 Stellar evolution (continued)
 Stages
•

Protostar
•
•
•

•
•
•
•

Gravitational contraction of gaseous cloud
continues
Core reaches 10 million K
Hydrogen nuclei fuse
• Become helium nuclei
• Process is called hydrogen burning
Energy is released
Outward pressure increases
Outward pressure balanced by gravity pulling in
Star becomes a stable main-sequence star

24.2 Stellar evolution (continued)
 Stages
•

Main-sequence stage
•

Stars age at different rates
• Massive stars use fuel faster and exist for
only a few million years
• Small stars use fuel slowly and exist for
perhaps hundreds of billions of years

•

90% of a star's life is in the main-sequence

24.2 Stellar evolution (continued)
 Stages
•

Red giant stage
•
•

•
•
•

Hydrogen burning migrates outward
Star's outer envelope expands
• Surface cools
• Surface becomes red
Core is collapsing as helium is converted to
carbon
Eventually all nuclear fuel is used
Gravity squeezes the star

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Low-mass star
• 0.5 solar mass
• Red giant collapses
• Becomes a white dwarf

24.2 Evolutionary stages of
low mass stars

Figure 24.12 A

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Medium-mass star
• Between 0.5 and 3 solar masses
• Red giant collapses
• Planetary nebula forms
• Becomes a white dwarf

24.2 Evolutionary stages of
medium mass stars

Figure 24.12 B

H-R diagram showing
stellar evolution

Figure 24.11

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Massive star
• Over 3 solar masses
• Short life span
• Terminates in a brilliant explosion called
a supernova
• Interior condenses
• May produce a hot, dense object that is
either a neutron star or a black hole

24.2 Evolutionary stages of
massive stars

Figure 24.12 C

24.2 Stellar remnants
 White
•
•

Small (some no larger than Earth)
Dense
•
•
•

•
•

dwarf

Can be more massive than the Sun
Spoonful weighs several tons
Atoms take up less space
• Electrons displaced inward
• Called degenerate matter

Hot surface
Cools to become a black dwarf

24.2 Stellar remnants (continued)
 Neutron
•

Forms from a more massive star
•
•

•
•

star

Star has more gravity
Squeezes itself smaller

Remnant of a supernova
Gravitational force collapses atoms
•
•

Electrons combine with protons to produce
neutrons
Small size

24.2 Stellar remnants (continued)
 Neutron
•

Pea size sample
•
•

•
•

star

Weighs 100 million tons
Same density as an atomic nucleus

Strong magnetic field
First one discovered in early 1970s
•
•

Pulsar (pulsating radio source)
Found in the Crab nebula (remnant of an A.D.
1054 supernova)

Crab Nebula in the
constellation Taurus

Figure 24.14

24.2 Stellar remnants (continued)
 Black
•
•

•

More dense than a neutron star
Intense surface gravity lets no light escape
As matter is pulled into it
•
•

•

hole

Becomes very hot
Emits x-rays

Likely candidate is Cygnus X-1, a strong xray source

Quiz Break

24.3 Galaxies
 Milky
•

Way galaxy

Structure
•
•

•
•

Determined by using radio telescopes
Large spiral galaxy
• About 100,000 light-years wide
• Thickness at the galactic nucleus is about
10,000 light-years
Three spiral arms of stars
Sun is 30,000 light-years from the center

Face-on view of the
Milk Way Galaxy

Figure 24.18 A

Edge-on view of the
Milk Way Galaxy

Figure 24.18 B

24.3 Galaxies (continued)
 Milky
•

Rotation
•
•
•

•

Way galaxy

Around the galactic nucleus
Outermost stars move the slowest
Sun rotates around the galactic nucleus once
about every 200 million years

Halo surrounds the galactic disk
•
•
•

Spherical
Very tenuous gas
Numerous globular clusters

24.3 Galaxies (continued)
 Other
•
•

galaxies

Existence was first proposed in mid-1700s
by Immanuel Kant
Four basic types of galaxies
•

Spiral galaxy
• Arms extending from nucleus
• About 30% of all galaxies
• Large diameter of 20,000 to 125,000 light
years
• Contains both young and old stars
• e.g., Milky Way

Great Galaxy, a spiral galaxy, in
the constellation Andromeda

Figure 24.20

24.3 Galaxies (continued)
 Other
•

galaxies

Four basic types of galaxies
•

•

Barred spiral galaxy
• Stars arranged in the shape of a bar
• Generally quite large
• About 10% of all galaxies
Elliptical galaxy
• Ellipsoidal shape
• About 60% of all galaxies
• Most are smaller than spiral galaxies;
however, they are also the largest known
galaxies

A barred spiral galaxy

Figure 24.22

24.3 Galaxies (continued)
 Other
•

galaxies

Four basic types of galaxies
•

Irregular galaxy
• Lacks symmetry
• About 10% of all galaxies
• Contains mostly young stars
• e.g., Magellanic Clouds

24.3 Galaxies (continued)
 Galactic
•
•
•

Group of galaxies
Some contain thousands of galaxies
Local Group
•
•

•

cluster

Our own group of galaxies
Contains at least 28 galaxies

Supercluster
•
•

Huge swarm of galaxies
May be the largest entity in the universe

Quiz Break

24.4 Red shifts
 Doppler
•

effect

Change in the wavelength of light emitted
by an object due to its motion
•

•

Movement away stretches the wavelength
• Longer wavelength
• Light appears redder
Movement toward “squeezes” the wavelength
• Shorter wavelength
• Light shifted toward the blue

24.4 Red shifts (continued)
 Doppler
•

effect

Amount of the Doppler shift indicates the
rate of movement
•
•

Large Doppler shift indicates a high velocity
Small Doppler shift indicates a lower velocity

 Expanding
•

universe

Most galaxies exhibit a red Doppler shift
•

Moving away

Raisin bread analogy of an
expanding universe

Figure 24.24

24.4 Red shifts (continued)
 Expanding
•

universe

Most galaxies exhibit a red Doppler shift
•

•
•
•

Far galaxies
• Exhibit the greatest shift
• Greater velocity
Discovered in 1929 by Edwin Hubble
Hubble's Law – the recessional speed of
galaxies is proportional to their distance
Accounts for red shifts

24.4 Big Bang theory
 Accounts

for galaxies moving away

from us
 Universe was once confined to a "ball"
that was
•
•

•

Supermassive
Dense
Hot

24.4 Big Bang theory (continued)
 Big

Bang marks the inception of the
universe
•
•

Occurred about 15 billion years ago
All matter and space was created

 Matter

is moving outward
 Fate of the universe
•

Two possibilities
•
•

Universe will last forever
Outward expansion sill stop and gravitational;
contraction will follow

24.4 Big Bang theory (continued)
 Fate
•

of the universe

Final fate depends on the average density
of the universe
•
•

If the density is more than the critical density,
then the universe would contract
Current estimates point to less then the critical
density and predict an ever-expanding, or
open, universe

Chapter 24Test Guidance
You will be responsible on the test for answering 3 of the following 6
questions.
1.

2.

3.
4.
5.
6.

What causes the difference between a star’s apparent
magnitude and it absolute magnitude.
List and explain the three factors that control the apparent
brightness of a star as seen from Earth.
Describe how binary stars are used to determine stellar mass.
List and describe the four basic types of galaxies.
What is Hubble’s Law, please explain in detail.
Briefly describe the Big Bang Theory (not the TV show).

End of Chapter 24


Slide 51

Lecture Outlines
PowerPoint

Chapter 24
Earth Science 11e
Tarbuck/Lutgens
Modified for educational
purposes only
By S. Koziol 12-8-2010

© 2006 Pearson Prentice Hall

Earth Science, 11e
Beyond Our
Solar System
Chapter 24

24.1 Properties of stars
 Distance
•
•

Measuring a star's distance can be very
difficult
Stellar parallax
•
•
•

•
•

Used for measuring distance to a star
Apparent shift in a star's position due to the
orbital motion of Earth
Measured as an angle
Near stars have the largest parallax
Largest parallax is less than one second of arc

24. 1 Properties of stars
(continued)

 Distance
•
•

Distances to the stars are very large
Units of measurement
•
•

•

Kilometers or astronomical units are too
cumbersome to use
Light-year is used most often
• Distance that light travels in 1 year
• One light-year is 9.5 trillion km (5.8 trillion
miles)

Other methods for measuring distance are
also used

24. 1 Properties of stars
(continued)

 Stellar
•

Controlled by three factors
•

•
•

•

brightness

Size
Temperature
Distance

Magnitude
•

Measure of a star's brightness

24.1 Properties of stars
(continued)

 Stellar
•

brightness

Magnitude
•

Two types of measurement
• Apparent magnitude
• Brightness when a star is viewed from
Earth
• Decreases with distance
• Numbers are used to designate
magnitudes - dim stars have large
numbers and negative numbers are also
used

24.1 Properties of stars
(continued)

 Stellar
•

brightness

Magnitude
•

Two types of measurement
• Absolute magnitude
• "True" or intrinsic brightness of a star
• Brightness at a standard distance of
32.6 light-years
• Most stars' absolute magnitudes are
between -5 and +15

24.1 Properties of stars
(continued)

 Color
•

Hot star
•

•
•

•

and temperature

Temperature above 30,000 K
Emits short-wavelength light
Appears blue

Cool star
•
•
•

Temperature less than 3000 K
Emits longer-wavelength light
Appears red

24.1 Properties of stars
(continued)

 Color
•

and temperature

Between 5000 and 6000 K
•
•

Stars appear yellow
e.g., Sun

 Binary
•

stars and stellar mass

Binary stars
•

Two stars orbiting one another
• Stars are held together by mutual
gravitation
• Both orbit around a common center of mass

24.1 Properties of stars (continued)
 Binary
•

Binary stars
•

•
•

•

stars and stellar mass

Visual binaries are resolved telescopically
More than 50% of the stars in the universe are
binary stars
Used to determine stellar mass

Stellar mass
•

Determined using binary stars – the center of
mass is closest to the most massive star

Binary stars
orbit each
other around
their common
center of
mass
Figure 24.4

24.1 Properties of stars (continued)
 Binary
•

stars and stellar mass

Stellar mass
•

Mass of most stars is between one-tenth and
fifty times the mass of the Sun

24.1 Hertzsprung-Russell
diagram
 Shows
•
•

the relation between stellar

Brightness (absolute magnitude) and
Temperature

 Diagram

is made by plotting (graphing)
each star's
•
•

Luminosity (brightness) and
Temperature

24.1 Hertzsprung-Russell
diagram (continued)
 Parts
•

Main-sequence stars
•

•
•

•

of an H-R diagram

90% of all stars
Band through the center of the H-R diagram
Sun is in the main-sequence

Giants (or red giants)
•
•
•

Very luminous
Large
Upper-right on the H-R diagram

24.1 Hertzsprung-Russell
diagram (continued)
 Parts
•

Giants (or red giants)
•

•

•

of an H-R diagram

Very large giants are called supergiants
Only a few percent of all stars

White dwarfs
•
•

•
•
•

Fainter than main-sequence stars
Small (approximate the size of Earth)
Lower-central area on the H-R diagram
Not all are white in color
Perhaps 10% of all stars

Idealized HertzsprungRussell diagram

Figure 24.5

Quiz Break

24.2 Variable stars
 Stars

that fluctuate in brightness
 Types of variable stars
•

Pulsating variables
•
•

•

Fluctuate regularly in brightness
Expand and contract in size

Eruptive variables
•
•
•

Explosive event
Sudden brightening
Called a nova

24.2 Interstellar matter
 Between

the stars is "the vacuum of

space"
 Nebula
•
•

Cloud of dust and gases
Two major types of nebulae
•

Bright nebula
• Glows if it close to a very hot star
• Two types of bright nebulae
• Emission nebula
• Reflection nebula

The Orion Nebula is a wellknown emission nebula

Figure 24.8

A faint blue reflection nebula in
the Pleiades star cluster

Figure 24.9

24.2 Interstellar matter (continued)
 Nebula
•

Two major types of nebulae
•

Dark nebula
• Not close to any bright star
• Appear dark
• Contains the material that forms stars and
planets

24.2 Stellar evolution
 Stars

exist because of gravity
 Two opposing forces in a star are
•
•

Gravity – contracts
Thermal nuclear energy – expands

 Stages
•

Birth
•

•
•
•
•

In dark, cool, interstellar clouds
Gravity contracts the cloud
Temperature rises
Radiates long-wavelength (red) light
Becomes a protostar

24.2 Stellar evolution (continued)
 Stages
•

Protostar
•
•
•

•
•
•
•

Gravitational contraction of gaseous cloud
continues
Core reaches 10 million K
Hydrogen nuclei fuse
• Become helium nuclei
• Process is called hydrogen burning
Energy is released
Outward pressure increases
Outward pressure balanced by gravity pulling in
Star becomes a stable main-sequence star

24.2 Stellar evolution (continued)
 Stages
•

Main-sequence stage
•

Stars age at different rates
• Massive stars use fuel faster and exist for
only a few million years
• Small stars use fuel slowly and exist for
perhaps hundreds of billions of years

•

90% of a star's life is in the main-sequence

24.2 Stellar evolution (continued)
 Stages
•

Red giant stage
•
•

•
•
•

Hydrogen burning migrates outward
Star's outer envelope expands
• Surface cools
• Surface becomes red
Core is collapsing as helium is converted to
carbon
Eventually all nuclear fuel is used
Gravity squeezes the star

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Low-mass star
• 0.5 solar mass
• Red giant collapses
• Becomes a white dwarf

24.2 Evolutionary stages of
low mass stars

Figure 24.12 A

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Medium-mass star
• Between 0.5 and 3 solar masses
• Red giant collapses
• Planetary nebula forms
• Becomes a white dwarf

24.2 Evolutionary stages of
medium mass stars

Figure 24.12 B

H-R diagram showing
stellar evolution

Figure 24.11

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Massive star
• Over 3 solar masses
• Short life span
• Terminates in a brilliant explosion called
a supernova
• Interior condenses
• May produce a hot, dense object that is
either a neutron star or a black hole

24.2 Evolutionary stages of
massive stars

Figure 24.12 C

24.2 Stellar remnants
 White
•
•

Small (some no larger than Earth)
Dense
•
•
•

•
•

dwarf

Can be more massive than the Sun
Spoonful weighs several tons
Atoms take up less space
• Electrons displaced inward
• Called degenerate matter

Hot surface
Cools to become a black dwarf

24.2 Stellar remnants (continued)
 Neutron
•

Forms from a more massive star
•
•

•
•

star

Star has more gravity
Squeezes itself smaller

Remnant of a supernova
Gravitational force collapses atoms
•
•

Electrons combine with protons to produce
neutrons
Small size

24.2 Stellar remnants (continued)
 Neutron
•

Pea size sample
•
•

•
•

star

Weighs 100 million tons
Same density as an atomic nucleus

Strong magnetic field
First one discovered in early 1970s
•
•

Pulsar (pulsating radio source)
Found in the Crab nebula (remnant of an A.D.
1054 supernova)

Crab Nebula in the
constellation Taurus

Figure 24.14

24.2 Stellar remnants (continued)
 Black
•
•

•

More dense than a neutron star
Intense surface gravity lets no light escape
As matter is pulled into it
•
•

•

hole

Becomes very hot
Emits x-rays

Likely candidate is Cygnus X-1, a strong xray source

Quiz Break

24.3 Galaxies
 Milky
•

Way galaxy

Structure
•
•

•
•

Determined by using radio telescopes
Large spiral galaxy
• About 100,000 light-years wide
• Thickness at the galactic nucleus is about
10,000 light-years
Three spiral arms of stars
Sun is 30,000 light-years from the center

Face-on view of the
Milk Way Galaxy

Figure 24.18 A

Edge-on view of the
Milk Way Galaxy

Figure 24.18 B

24.3 Galaxies (continued)
 Milky
•

Rotation
•
•
•

•

Way galaxy

Around the galactic nucleus
Outermost stars move the slowest
Sun rotates around the galactic nucleus once
about every 200 million years

Halo surrounds the galactic disk
•
•
•

Spherical
Very tenuous gas
Numerous globular clusters

24.3 Galaxies (continued)
 Other
•
•

galaxies

Existence was first proposed in mid-1700s
by Immanuel Kant
Four basic types of galaxies
•

Spiral galaxy
• Arms extending from nucleus
• About 30% of all galaxies
• Large diameter of 20,000 to 125,000 light
years
• Contains both young and old stars
• e.g., Milky Way

Great Galaxy, a spiral galaxy, in
the constellation Andromeda

Figure 24.20

24.3 Galaxies (continued)
 Other
•

galaxies

Four basic types of galaxies
•

•

Barred spiral galaxy
• Stars arranged in the shape of a bar
• Generally quite large
• About 10% of all galaxies
Elliptical galaxy
• Ellipsoidal shape
• About 60% of all galaxies
• Most are smaller than spiral galaxies;
however, they are also the largest known
galaxies

A barred spiral galaxy

Figure 24.22

24.3 Galaxies (continued)
 Other
•

galaxies

Four basic types of galaxies
•

Irregular galaxy
• Lacks symmetry
• About 10% of all galaxies
• Contains mostly young stars
• e.g., Magellanic Clouds

24.3 Galaxies (continued)
 Galactic
•
•
•

Group of galaxies
Some contain thousands of galaxies
Local Group
•
•

•

cluster

Our own group of galaxies
Contains at least 28 galaxies

Supercluster
•
•

Huge swarm of galaxies
May be the largest entity in the universe

Quiz Break

24.4 Red shifts
 Doppler
•

effect

Change in the wavelength of light emitted
by an object due to its motion
•

•

Movement away stretches the wavelength
• Longer wavelength
• Light appears redder
Movement toward “squeezes” the wavelength
• Shorter wavelength
• Light shifted toward the blue

24.4 Red shifts (continued)
 Doppler
•

effect

Amount of the Doppler shift indicates the
rate of movement
•
•

Large Doppler shift indicates a high velocity
Small Doppler shift indicates a lower velocity

 Expanding
•

universe

Most galaxies exhibit a red Doppler shift
•

Moving away

Raisin bread analogy of an
expanding universe

Figure 24.24

24.4 Red shifts (continued)
 Expanding
•

universe

Most galaxies exhibit a red Doppler shift
•

•
•
•

Far galaxies
• Exhibit the greatest shift
• Greater velocity
Discovered in 1929 by Edwin Hubble
Hubble's Law – the recessional speed of
galaxies is proportional to their distance
Accounts for red shifts

24.4 Big Bang theory
 Accounts

for galaxies moving away

from us
 Universe was once confined to a "ball"
that was
•
•

•

Supermassive
Dense
Hot

24.4 Big Bang theory (continued)
 Big

Bang marks the inception of the
universe
•
•

Occurred about 15 billion years ago
All matter and space was created

 Matter

is moving outward
 Fate of the universe
•

Two possibilities
•
•

Universe will last forever
Outward expansion sill stop and gravitational;
contraction will follow

24.4 Big Bang theory (continued)
 Fate
•

of the universe

Final fate depends on the average density
of the universe
•
•

If the density is more than the critical density,
then the universe would contract
Current estimates point to less then the critical
density and predict an ever-expanding, or
open, universe

Chapter 24Test Guidance
You will be responsible on the test for answering 3 of the following 6
questions.
1.

2.

3.
4.
5.
6.

What causes the difference between a star’s apparent
magnitude and it absolute magnitude.
List and explain the three factors that control the apparent
brightness of a star as seen from Earth.
Describe how binary stars are used to determine stellar mass.
List and describe the four basic types of galaxies.
What is Hubble’s Law, please explain in detail.
Briefly describe the Big Bang Theory (not the TV show).

End of Chapter 24


Slide 52

Lecture Outlines
PowerPoint

Chapter 24
Earth Science 11e
Tarbuck/Lutgens
Modified for educational
purposes only
By S. Koziol 12-8-2010

© 2006 Pearson Prentice Hall

Earth Science, 11e
Beyond Our
Solar System
Chapter 24

24.1 Properties of stars
 Distance
•
•

Measuring a star's distance can be very
difficult
Stellar parallax
•
•
•

•
•

Used for measuring distance to a star
Apparent shift in a star's position due to the
orbital motion of Earth
Measured as an angle
Near stars have the largest parallax
Largest parallax is less than one second of arc

24. 1 Properties of stars
(continued)

 Distance
•
•

Distances to the stars are very large
Units of measurement
•
•

•

Kilometers or astronomical units are too
cumbersome to use
Light-year is used most often
• Distance that light travels in 1 year
• One light-year is 9.5 trillion km (5.8 trillion
miles)

Other methods for measuring distance are
also used

24. 1 Properties of stars
(continued)

 Stellar
•

Controlled by three factors
•

•
•

•

brightness

Size
Temperature
Distance

Magnitude
•

Measure of a star's brightness

24.1 Properties of stars
(continued)

 Stellar
•

brightness

Magnitude
•

Two types of measurement
• Apparent magnitude
• Brightness when a star is viewed from
Earth
• Decreases with distance
• Numbers are used to designate
magnitudes - dim stars have large
numbers and negative numbers are also
used

24.1 Properties of stars
(continued)

 Stellar
•

brightness

Magnitude
•

Two types of measurement
• Absolute magnitude
• "True" or intrinsic brightness of a star
• Brightness at a standard distance of
32.6 light-years
• Most stars' absolute magnitudes are
between -5 and +15

24.1 Properties of stars
(continued)

 Color
•

Hot star
•

•
•

•

and temperature

Temperature above 30,000 K
Emits short-wavelength light
Appears blue

Cool star
•
•
•

Temperature less than 3000 K
Emits longer-wavelength light
Appears red

24.1 Properties of stars
(continued)

 Color
•

and temperature

Between 5000 and 6000 K
•
•

Stars appear yellow
e.g., Sun

 Binary
•

stars and stellar mass

Binary stars
•

Two stars orbiting one another
• Stars are held together by mutual
gravitation
• Both orbit around a common center of mass

24.1 Properties of stars (continued)
 Binary
•

Binary stars
•

•
•

•

stars and stellar mass

Visual binaries are resolved telescopically
More than 50% of the stars in the universe are
binary stars
Used to determine stellar mass

Stellar mass
•

Determined using binary stars – the center of
mass is closest to the most massive star

Binary stars
orbit each
other around
their common
center of
mass
Figure 24.4

24.1 Properties of stars (continued)
 Binary
•

stars and stellar mass

Stellar mass
•

Mass of most stars is between one-tenth and
fifty times the mass of the Sun

24.1 Hertzsprung-Russell
diagram
 Shows
•
•

the relation between stellar

Brightness (absolute magnitude) and
Temperature

 Diagram

is made by plotting (graphing)
each star's
•
•

Luminosity (brightness) and
Temperature

24.1 Hertzsprung-Russell
diagram (continued)
 Parts
•

Main-sequence stars
•

•
•

•

of an H-R diagram

90% of all stars
Band through the center of the H-R diagram
Sun is in the main-sequence

Giants (or red giants)
•
•
•

Very luminous
Large
Upper-right on the H-R diagram

24.1 Hertzsprung-Russell
diagram (continued)
 Parts
•

Giants (or red giants)
•

•

•

of an H-R diagram

Very large giants are called supergiants
Only a few percent of all stars

White dwarfs
•
•

•
•
•

Fainter than main-sequence stars
Small (approximate the size of Earth)
Lower-central area on the H-R diagram
Not all are white in color
Perhaps 10% of all stars

Idealized HertzsprungRussell diagram

Figure 24.5

Quiz Break

24.2 Variable stars
 Stars

that fluctuate in brightness
 Types of variable stars
•

Pulsating variables
•
•

•

Fluctuate regularly in brightness
Expand and contract in size

Eruptive variables
•
•
•

Explosive event
Sudden brightening
Called a nova

24.2 Interstellar matter
 Between

the stars is "the vacuum of

space"
 Nebula
•
•

Cloud of dust and gases
Two major types of nebulae
•

Bright nebula
• Glows if it close to a very hot star
• Two types of bright nebulae
• Emission nebula
• Reflection nebula

The Orion Nebula is a wellknown emission nebula

Figure 24.8

A faint blue reflection nebula in
the Pleiades star cluster

Figure 24.9

24.2 Interstellar matter (continued)
 Nebula
•

Two major types of nebulae
•

Dark nebula
• Not close to any bright star
• Appear dark
• Contains the material that forms stars and
planets

24.2 Stellar evolution
 Stars

exist because of gravity
 Two opposing forces in a star are
•
•

Gravity – contracts
Thermal nuclear energy – expands

 Stages
•

Birth
•

•
•
•
•

In dark, cool, interstellar clouds
Gravity contracts the cloud
Temperature rises
Radiates long-wavelength (red) light
Becomes a protostar

24.2 Stellar evolution (continued)
 Stages
•

Protostar
•
•
•

•
•
•
•

Gravitational contraction of gaseous cloud
continues
Core reaches 10 million K
Hydrogen nuclei fuse
• Become helium nuclei
• Process is called hydrogen burning
Energy is released
Outward pressure increases
Outward pressure balanced by gravity pulling in
Star becomes a stable main-sequence star

24.2 Stellar evolution (continued)
 Stages
•

Main-sequence stage
•

Stars age at different rates
• Massive stars use fuel faster and exist for
only a few million years
• Small stars use fuel slowly and exist for
perhaps hundreds of billions of years

•

90% of a star's life is in the main-sequence

24.2 Stellar evolution (continued)
 Stages
•

Red giant stage
•
•

•
•
•

Hydrogen burning migrates outward
Star's outer envelope expands
• Surface cools
• Surface becomes red
Core is collapsing as helium is converted to
carbon
Eventually all nuclear fuel is used
Gravity squeezes the star

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Low-mass star
• 0.5 solar mass
• Red giant collapses
• Becomes a white dwarf

24.2 Evolutionary stages of
low mass stars

Figure 24.12 A

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Medium-mass star
• Between 0.5 and 3 solar masses
• Red giant collapses
• Planetary nebula forms
• Becomes a white dwarf

24.2 Evolutionary stages of
medium mass stars

Figure 24.12 B

H-R diagram showing
stellar evolution

Figure 24.11

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Massive star
• Over 3 solar masses
• Short life span
• Terminates in a brilliant explosion called
a supernova
• Interior condenses
• May produce a hot, dense object that is
either a neutron star or a black hole

24.2 Evolutionary stages of
massive stars

Figure 24.12 C

24.2 Stellar remnants
 White
•
•

Small (some no larger than Earth)
Dense
•
•
•

•
•

dwarf

Can be more massive than the Sun
Spoonful weighs several tons
Atoms take up less space
• Electrons displaced inward
• Called degenerate matter

Hot surface
Cools to become a black dwarf

24.2 Stellar remnants (continued)
 Neutron
•

Forms from a more massive star
•
•

•
•

star

Star has more gravity
Squeezes itself smaller

Remnant of a supernova
Gravitational force collapses atoms
•
•

Electrons combine with protons to produce
neutrons
Small size

24.2 Stellar remnants (continued)
 Neutron
•

Pea size sample
•
•

•
•

star

Weighs 100 million tons
Same density as an atomic nucleus

Strong magnetic field
First one discovered in early 1970s
•
•

Pulsar (pulsating radio source)
Found in the Crab nebula (remnant of an A.D.
1054 supernova)

Crab Nebula in the
constellation Taurus

Figure 24.14

24.2 Stellar remnants (continued)
 Black
•
•

•

More dense than a neutron star
Intense surface gravity lets no light escape
As matter is pulled into it
•
•

•

hole

Becomes very hot
Emits x-rays

Likely candidate is Cygnus X-1, a strong xray source

Quiz Break

24.3 Galaxies
 Milky
•

Way galaxy

Structure
•
•

•
•

Determined by using radio telescopes
Large spiral galaxy
• About 100,000 light-years wide
• Thickness at the galactic nucleus is about
10,000 light-years
Three spiral arms of stars
Sun is 30,000 light-years from the center

Face-on view of the
Milk Way Galaxy

Figure 24.18 A

Edge-on view of the
Milk Way Galaxy

Figure 24.18 B

24.3 Galaxies (continued)
 Milky
•

Rotation
•
•
•

•

Way galaxy

Around the galactic nucleus
Outermost stars move the slowest
Sun rotates around the galactic nucleus once
about every 200 million years

Halo surrounds the galactic disk
•
•
•

Spherical
Very tenuous gas
Numerous globular clusters

24.3 Galaxies (continued)
 Other
•
•

galaxies

Existence was first proposed in mid-1700s
by Immanuel Kant
Four basic types of galaxies
•

Spiral galaxy
• Arms extending from nucleus
• About 30% of all galaxies
• Large diameter of 20,000 to 125,000 light
years
• Contains both young and old stars
• e.g., Milky Way

Great Galaxy, a spiral galaxy, in
the constellation Andromeda

Figure 24.20

24.3 Galaxies (continued)
 Other
•

galaxies

Four basic types of galaxies
•

•

Barred spiral galaxy
• Stars arranged in the shape of a bar
• Generally quite large
• About 10% of all galaxies
Elliptical galaxy
• Ellipsoidal shape
• About 60% of all galaxies
• Most are smaller than spiral galaxies;
however, they are also the largest known
galaxies

A barred spiral galaxy

Figure 24.22

24.3 Galaxies (continued)
 Other
•

galaxies

Four basic types of galaxies
•

Irregular galaxy
• Lacks symmetry
• About 10% of all galaxies
• Contains mostly young stars
• e.g., Magellanic Clouds

24.3 Galaxies (continued)
 Galactic
•
•
•

Group of galaxies
Some contain thousands of galaxies
Local Group
•
•

•

cluster

Our own group of galaxies
Contains at least 28 galaxies

Supercluster
•
•

Huge swarm of galaxies
May be the largest entity in the universe

Quiz Break

24.4 Red shifts
 Doppler
•

effect

Change in the wavelength of light emitted
by an object due to its motion
•

•

Movement away stretches the wavelength
• Longer wavelength
• Light appears redder
Movement toward “squeezes” the wavelength
• Shorter wavelength
• Light shifted toward the blue

24.4 Red shifts (continued)
 Doppler
•

effect

Amount of the Doppler shift indicates the
rate of movement
•
•

Large Doppler shift indicates a high velocity
Small Doppler shift indicates a lower velocity

 Expanding
•

universe

Most galaxies exhibit a red Doppler shift
•

Moving away

Raisin bread analogy of an
expanding universe

Figure 24.24

24.4 Red shifts (continued)
 Expanding
•

universe

Most galaxies exhibit a red Doppler shift
•

•
•
•

Far galaxies
• Exhibit the greatest shift
• Greater velocity
Discovered in 1929 by Edwin Hubble
Hubble's Law – the recessional speed of
galaxies is proportional to their distance
Accounts for red shifts

24.4 Big Bang theory
 Accounts

for galaxies moving away

from us
 Universe was once confined to a "ball"
that was
•
•

•

Supermassive
Dense
Hot

24.4 Big Bang theory (continued)
 Big

Bang marks the inception of the
universe
•
•

Occurred about 15 billion years ago
All matter and space was created

 Matter

is moving outward
 Fate of the universe
•

Two possibilities
•
•

Universe will last forever
Outward expansion sill stop and gravitational;
contraction will follow

24.4 Big Bang theory (continued)
 Fate
•

of the universe

Final fate depends on the average density
of the universe
•
•

If the density is more than the critical density,
then the universe would contract
Current estimates point to less then the critical
density and predict an ever-expanding, or
open, universe

Chapter 24Test Guidance
You will be responsible on the test for answering 3 of the following 6
questions.
1.

2.

3.
4.
5.
6.

What causes the difference between a star’s apparent
magnitude and it absolute magnitude.
List and explain the three factors that control the apparent
brightness of a star as seen from Earth.
Describe how binary stars are used to determine stellar mass.
List and describe the four basic types of galaxies.
What is Hubble’s Law, please explain in detail.
Briefly describe the Big Bang Theory (not the TV show).

End of Chapter 24


Slide 53

Lecture Outlines
PowerPoint

Chapter 24
Earth Science 11e
Tarbuck/Lutgens
Modified for educational
purposes only
By S. Koziol 12-8-2010

© 2006 Pearson Prentice Hall

Earth Science, 11e
Beyond Our
Solar System
Chapter 24

24.1 Properties of stars
 Distance
•
•

Measuring a star's distance can be very
difficult
Stellar parallax
•
•
•

•
•

Used for measuring distance to a star
Apparent shift in a star's position due to the
orbital motion of Earth
Measured as an angle
Near stars have the largest parallax
Largest parallax is less than one second of arc

24. 1 Properties of stars
(continued)

 Distance
•
•

Distances to the stars are very large
Units of measurement
•
•

•

Kilometers or astronomical units are too
cumbersome to use
Light-year is used most often
• Distance that light travels in 1 year
• One light-year is 9.5 trillion km (5.8 trillion
miles)

Other methods for measuring distance are
also used

24. 1 Properties of stars
(continued)

 Stellar
•

Controlled by three factors
•

•
•

•

brightness

Size
Temperature
Distance

Magnitude
•

Measure of a star's brightness

24.1 Properties of stars
(continued)

 Stellar
•

brightness

Magnitude
•

Two types of measurement
• Apparent magnitude
• Brightness when a star is viewed from
Earth
• Decreases with distance
• Numbers are used to designate
magnitudes - dim stars have large
numbers and negative numbers are also
used

24.1 Properties of stars
(continued)

 Stellar
•

brightness

Magnitude
•

Two types of measurement
• Absolute magnitude
• "True" or intrinsic brightness of a star
• Brightness at a standard distance of
32.6 light-years
• Most stars' absolute magnitudes are
between -5 and +15

24.1 Properties of stars
(continued)

 Color
•

Hot star
•

•
•

•

and temperature

Temperature above 30,000 K
Emits short-wavelength light
Appears blue

Cool star
•
•
•

Temperature less than 3000 K
Emits longer-wavelength light
Appears red

24.1 Properties of stars
(continued)

 Color
•

and temperature

Between 5000 and 6000 K
•
•

Stars appear yellow
e.g., Sun

 Binary
•

stars and stellar mass

Binary stars
•

Two stars orbiting one another
• Stars are held together by mutual
gravitation
• Both orbit around a common center of mass

24.1 Properties of stars (continued)
 Binary
•

Binary stars
•

•
•

•

stars and stellar mass

Visual binaries are resolved telescopically
More than 50% of the stars in the universe are
binary stars
Used to determine stellar mass

Stellar mass
•

Determined using binary stars – the center of
mass is closest to the most massive star

Binary stars
orbit each
other around
their common
center of
mass
Figure 24.4

24.1 Properties of stars (continued)
 Binary
•

stars and stellar mass

Stellar mass
•

Mass of most stars is between one-tenth and
fifty times the mass of the Sun

24.1 Hertzsprung-Russell
diagram
 Shows
•
•

the relation between stellar

Brightness (absolute magnitude) and
Temperature

 Diagram

is made by plotting (graphing)
each star's
•
•

Luminosity (brightness) and
Temperature

24.1 Hertzsprung-Russell
diagram (continued)
 Parts
•

Main-sequence stars
•

•
•

•

of an H-R diagram

90% of all stars
Band through the center of the H-R diagram
Sun is in the main-sequence

Giants (or red giants)
•
•
•

Very luminous
Large
Upper-right on the H-R diagram

24.1 Hertzsprung-Russell
diagram (continued)
 Parts
•

Giants (or red giants)
•

•

•

of an H-R diagram

Very large giants are called supergiants
Only a few percent of all stars

White dwarfs
•
•

•
•
•

Fainter than main-sequence stars
Small (approximate the size of Earth)
Lower-central area on the H-R diagram
Not all are white in color
Perhaps 10% of all stars

Idealized HertzsprungRussell diagram

Figure 24.5

Quiz Break

24.2 Variable stars
 Stars

that fluctuate in brightness
 Types of variable stars
•

Pulsating variables
•
•

•

Fluctuate regularly in brightness
Expand and contract in size

Eruptive variables
•
•
•

Explosive event
Sudden brightening
Called a nova

24.2 Interstellar matter
 Between

the stars is "the vacuum of

space"
 Nebula
•
•

Cloud of dust and gases
Two major types of nebulae
•

Bright nebula
• Glows if it close to a very hot star
• Two types of bright nebulae
• Emission nebula
• Reflection nebula

The Orion Nebula is a wellknown emission nebula

Figure 24.8

A faint blue reflection nebula in
the Pleiades star cluster

Figure 24.9

24.2 Interstellar matter (continued)
 Nebula
•

Two major types of nebulae
•

Dark nebula
• Not close to any bright star
• Appear dark
• Contains the material that forms stars and
planets

24.2 Stellar evolution
 Stars

exist because of gravity
 Two opposing forces in a star are
•
•

Gravity – contracts
Thermal nuclear energy – expands

 Stages
•

Birth
•

•
•
•
•

In dark, cool, interstellar clouds
Gravity contracts the cloud
Temperature rises
Radiates long-wavelength (red) light
Becomes a protostar

24.2 Stellar evolution (continued)
 Stages
•

Protostar
•
•
•

•
•
•
•

Gravitational contraction of gaseous cloud
continues
Core reaches 10 million K
Hydrogen nuclei fuse
• Become helium nuclei
• Process is called hydrogen burning
Energy is released
Outward pressure increases
Outward pressure balanced by gravity pulling in
Star becomes a stable main-sequence star

24.2 Stellar evolution (continued)
 Stages
•

Main-sequence stage
•

Stars age at different rates
• Massive stars use fuel faster and exist for
only a few million years
• Small stars use fuel slowly and exist for
perhaps hundreds of billions of years

•

90% of a star's life is in the main-sequence

24.2 Stellar evolution (continued)
 Stages
•

Red giant stage
•
•

•
•
•

Hydrogen burning migrates outward
Star's outer envelope expands
• Surface cools
• Surface becomes red
Core is collapsing as helium is converted to
carbon
Eventually all nuclear fuel is used
Gravity squeezes the star

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Low-mass star
• 0.5 solar mass
• Red giant collapses
• Becomes a white dwarf

24.2 Evolutionary stages of
low mass stars

Figure 24.12 A

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Medium-mass star
• Between 0.5 and 3 solar masses
• Red giant collapses
• Planetary nebula forms
• Becomes a white dwarf

24.2 Evolutionary stages of
medium mass stars

Figure 24.12 B

H-R diagram showing
stellar evolution

Figure 24.11

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Massive star
• Over 3 solar masses
• Short life span
• Terminates in a brilliant explosion called
a supernova
• Interior condenses
• May produce a hot, dense object that is
either a neutron star or a black hole

24.2 Evolutionary stages of
massive stars

Figure 24.12 C

24.2 Stellar remnants
 White
•
•

Small (some no larger than Earth)
Dense
•
•
•

•
•

dwarf

Can be more massive than the Sun
Spoonful weighs several tons
Atoms take up less space
• Electrons displaced inward
• Called degenerate matter

Hot surface
Cools to become a black dwarf

24.2 Stellar remnants (continued)
 Neutron
•

Forms from a more massive star
•
•

•
•

star

Star has more gravity
Squeezes itself smaller

Remnant of a supernova
Gravitational force collapses atoms
•
•

Electrons combine with protons to produce
neutrons
Small size

24.2 Stellar remnants (continued)
 Neutron
•

Pea size sample
•
•

•
•

star

Weighs 100 million tons
Same density as an atomic nucleus

Strong magnetic field
First one discovered in early 1970s
•
•

Pulsar (pulsating radio source)
Found in the Crab nebula (remnant of an A.D.
1054 supernova)

Crab Nebula in the
constellation Taurus

Figure 24.14

24.2 Stellar remnants (continued)
 Black
•
•

•

More dense than a neutron star
Intense surface gravity lets no light escape
As matter is pulled into it
•
•

•

hole

Becomes very hot
Emits x-rays

Likely candidate is Cygnus X-1, a strong xray source

Quiz Break

24.3 Galaxies
 Milky
•

Way galaxy

Structure
•
•

•
•

Determined by using radio telescopes
Large spiral galaxy
• About 100,000 light-years wide
• Thickness at the galactic nucleus is about
10,000 light-years
Three spiral arms of stars
Sun is 30,000 light-years from the center

Face-on view of the
Milk Way Galaxy

Figure 24.18 A

Edge-on view of the
Milk Way Galaxy

Figure 24.18 B

24.3 Galaxies (continued)
 Milky
•

Rotation
•
•
•

•

Way galaxy

Around the galactic nucleus
Outermost stars move the slowest
Sun rotates around the galactic nucleus once
about every 200 million years

Halo surrounds the galactic disk
•
•
•

Spherical
Very tenuous gas
Numerous globular clusters

24.3 Galaxies (continued)
 Other
•
•

galaxies

Existence was first proposed in mid-1700s
by Immanuel Kant
Four basic types of galaxies
•

Spiral galaxy
• Arms extending from nucleus
• About 30% of all galaxies
• Large diameter of 20,000 to 125,000 light
years
• Contains both young and old stars
• e.g., Milky Way

Great Galaxy, a spiral galaxy, in
the constellation Andromeda

Figure 24.20

24.3 Galaxies (continued)
 Other
•

galaxies

Four basic types of galaxies
•

•

Barred spiral galaxy
• Stars arranged in the shape of a bar
• Generally quite large
• About 10% of all galaxies
Elliptical galaxy
• Ellipsoidal shape
• About 60% of all galaxies
• Most are smaller than spiral galaxies;
however, they are also the largest known
galaxies

A barred spiral galaxy

Figure 24.22

24.3 Galaxies (continued)
 Other
•

galaxies

Four basic types of galaxies
•

Irregular galaxy
• Lacks symmetry
• About 10% of all galaxies
• Contains mostly young stars
• e.g., Magellanic Clouds

24.3 Galaxies (continued)
 Galactic
•
•
•

Group of galaxies
Some contain thousands of galaxies
Local Group
•
•

•

cluster

Our own group of galaxies
Contains at least 28 galaxies

Supercluster
•
•

Huge swarm of galaxies
May be the largest entity in the universe

Quiz Break

24.4 Red shifts
 Doppler
•

effect

Change in the wavelength of light emitted
by an object due to its motion
•

•

Movement away stretches the wavelength
• Longer wavelength
• Light appears redder
Movement toward “squeezes” the wavelength
• Shorter wavelength
• Light shifted toward the blue

24.4 Red shifts (continued)
 Doppler
•

effect

Amount of the Doppler shift indicates the
rate of movement
•
•

Large Doppler shift indicates a high velocity
Small Doppler shift indicates a lower velocity

 Expanding
•

universe

Most galaxies exhibit a red Doppler shift
•

Moving away

Raisin bread analogy of an
expanding universe

Figure 24.24

24.4 Red shifts (continued)
 Expanding
•

universe

Most galaxies exhibit a red Doppler shift
•

•
•
•

Far galaxies
• Exhibit the greatest shift
• Greater velocity
Discovered in 1929 by Edwin Hubble
Hubble's Law – the recessional speed of
galaxies is proportional to their distance
Accounts for red shifts

24.4 Big Bang theory
 Accounts

for galaxies moving away

from us
 Universe was once confined to a "ball"
that was
•
•

•

Supermassive
Dense
Hot

24.4 Big Bang theory (continued)
 Big

Bang marks the inception of the
universe
•
•

Occurred about 15 billion years ago
All matter and space was created

 Matter

is moving outward
 Fate of the universe
•

Two possibilities
•
•

Universe will last forever
Outward expansion sill stop and gravitational;
contraction will follow

24.4 Big Bang theory (continued)
 Fate
•

of the universe

Final fate depends on the average density
of the universe
•
•

If the density is more than the critical density,
then the universe would contract
Current estimates point to less then the critical
density and predict an ever-expanding, or
open, universe

Chapter 24Test Guidance
You will be responsible on the test for answering 3 of the following 6
questions.
1.

2.

3.
4.
5.
6.

What causes the difference between a star’s apparent
magnitude and it absolute magnitude.
List and explain the three factors that control the apparent
brightness of a star as seen from Earth.
Describe how binary stars are used to determine stellar mass.
List and describe the four basic types of galaxies.
What is Hubble’s Law, please explain in detail.
Briefly describe the Big Bang Theory (not the TV show).

End of Chapter 24


Slide 54

Lecture Outlines
PowerPoint

Chapter 24
Earth Science 11e
Tarbuck/Lutgens
Modified for educational
purposes only
By S. Koziol 12-8-2010

© 2006 Pearson Prentice Hall

Earth Science, 11e
Beyond Our
Solar System
Chapter 24

24.1 Properties of stars
 Distance
•
•

Measuring a star's distance can be very
difficult
Stellar parallax
•
•
•

•
•

Used for measuring distance to a star
Apparent shift in a star's position due to the
orbital motion of Earth
Measured as an angle
Near stars have the largest parallax
Largest parallax is less than one second of arc

24. 1 Properties of stars
(continued)

 Distance
•
•

Distances to the stars are very large
Units of measurement
•
•

•

Kilometers or astronomical units are too
cumbersome to use
Light-year is used most often
• Distance that light travels in 1 year
• One light-year is 9.5 trillion km (5.8 trillion
miles)

Other methods for measuring distance are
also used

24. 1 Properties of stars
(continued)

 Stellar
•

Controlled by three factors
•

•
•

•

brightness

Size
Temperature
Distance

Magnitude
•

Measure of a star's brightness

24.1 Properties of stars
(continued)

 Stellar
•

brightness

Magnitude
•

Two types of measurement
• Apparent magnitude
• Brightness when a star is viewed from
Earth
• Decreases with distance
• Numbers are used to designate
magnitudes - dim stars have large
numbers and negative numbers are also
used

24.1 Properties of stars
(continued)

 Stellar
•

brightness

Magnitude
•

Two types of measurement
• Absolute magnitude
• "True" or intrinsic brightness of a star
• Brightness at a standard distance of
32.6 light-years
• Most stars' absolute magnitudes are
between -5 and +15

24.1 Properties of stars
(continued)

 Color
•

Hot star
•

•
•

•

and temperature

Temperature above 30,000 K
Emits short-wavelength light
Appears blue

Cool star
•
•
•

Temperature less than 3000 K
Emits longer-wavelength light
Appears red

24.1 Properties of stars
(continued)

 Color
•

and temperature

Between 5000 and 6000 K
•
•

Stars appear yellow
e.g., Sun

 Binary
•

stars and stellar mass

Binary stars
•

Two stars orbiting one another
• Stars are held together by mutual
gravitation
• Both orbit around a common center of mass

24.1 Properties of stars (continued)
 Binary
•

Binary stars
•

•
•

•

stars and stellar mass

Visual binaries are resolved telescopically
More than 50% of the stars in the universe are
binary stars
Used to determine stellar mass

Stellar mass
•

Determined using binary stars – the center of
mass is closest to the most massive star

Binary stars
orbit each
other around
their common
center of
mass
Figure 24.4

24.1 Properties of stars (continued)
 Binary
•

stars and stellar mass

Stellar mass
•

Mass of most stars is between one-tenth and
fifty times the mass of the Sun

24.1 Hertzsprung-Russell
diagram
 Shows
•
•

the relation between stellar

Brightness (absolute magnitude) and
Temperature

 Diagram

is made by plotting (graphing)
each star's
•
•

Luminosity (brightness) and
Temperature

24.1 Hertzsprung-Russell
diagram (continued)
 Parts
•

Main-sequence stars
•

•
•

•

of an H-R diagram

90% of all stars
Band through the center of the H-R diagram
Sun is in the main-sequence

Giants (or red giants)
•
•
•

Very luminous
Large
Upper-right on the H-R diagram

24.1 Hertzsprung-Russell
diagram (continued)
 Parts
•

Giants (or red giants)
•

•

•

of an H-R diagram

Very large giants are called supergiants
Only a few percent of all stars

White dwarfs
•
•

•
•
•

Fainter than main-sequence stars
Small (approximate the size of Earth)
Lower-central area on the H-R diagram
Not all are white in color
Perhaps 10% of all stars

Idealized HertzsprungRussell diagram

Figure 24.5

Quiz Break

24.2 Variable stars
 Stars

that fluctuate in brightness
 Types of variable stars
•

Pulsating variables
•
•

•

Fluctuate regularly in brightness
Expand and contract in size

Eruptive variables
•
•
•

Explosive event
Sudden brightening
Called a nova

24.2 Interstellar matter
 Between

the stars is "the vacuum of

space"
 Nebula
•
•

Cloud of dust and gases
Two major types of nebulae
•

Bright nebula
• Glows if it close to a very hot star
• Two types of bright nebulae
• Emission nebula
• Reflection nebula

The Orion Nebula is a wellknown emission nebula

Figure 24.8

A faint blue reflection nebula in
the Pleiades star cluster

Figure 24.9

24.2 Interstellar matter (continued)
 Nebula
•

Two major types of nebulae
•

Dark nebula
• Not close to any bright star
• Appear dark
• Contains the material that forms stars and
planets

24.2 Stellar evolution
 Stars

exist because of gravity
 Two opposing forces in a star are
•
•

Gravity – contracts
Thermal nuclear energy – expands

 Stages
•

Birth
•

•
•
•
•

In dark, cool, interstellar clouds
Gravity contracts the cloud
Temperature rises
Radiates long-wavelength (red) light
Becomes a protostar

24.2 Stellar evolution (continued)
 Stages
•

Protostar
•
•
•

•
•
•
•

Gravitational contraction of gaseous cloud
continues
Core reaches 10 million K
Hydrogen nuclei fuse
• Become helium nuclei
• Process is called hydrogen burning
Energy is released
Outward pressure increases
Outward pressure balanced by gravity pulling in
Star becomes a stable main-sequence star

24.2 Stellar evolution (continued)
 Stages
•

Main-sequence stage
•

Stars age at different rates
• Massive stars use fuel faster and exist for
only a few million years
• Small stars use fuel slowly and exist for
perhaps hundreds of billions of years

•

90% of a star's life is in the main-sequence

24.2 Stellar evolution (continued)
 Stages
•

Red giant stage
•
•

•
•
•

Hydrogen burning migrates outward
Star's outer envelope expands
• Surface cools
• Surface becomes red
Core is collapsing as helium is converted to
carbon
Eventually all nuclear fuel is used
Gravity squeezes the star

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Low-mass star
• 0.5 solar mass
• Red giant collapses
• Becomes a white dwarf

24.2 Evolutionary stages of
low mass stars

Figure 24.12 A

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Medium-mass star
• Between 0.5 and 3 solar masses
• Red giant collapses
• Planetary nebula forms
• Becomes a white dwarf

24.2 Evolutionary stages of
medium mass stars

Figure 24.12 B

H-R diagram showing
stellar evolution

Figure 24.11

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Massive star
• Over 3 solar masses
• Short life span
• Terminates in a brilliant explosion called
a supernova
• Interior condenses
• May produce a hot, dense object that is
either a neutron star or a black hole

24.2 Evolutionary stages of
massive stars

Figure 24.12 C

24.2 Stellar remnants
 White
•
•

Small (some no larger than Earth)
Dense
•
•
•

•
•

dwarf

Can be more massive than the Sun
Spoonful weighs several tons
Atoms take up less space
• Electrons displaced inward
• Called degenerate matter

Hot surface
Cools to become a black dwarf

24.2 Stellar remnants (continued)
 Neutron
•

Forms from a more massive star
•
•

•
•

star

Star has more gravity
Squeezes itself smaller

Remnant of a supernova
Gravitational force collapses atoms
•
•

Electrons combine with protons to produce
neutrons
Small size

24.2 Stellar remnants (continued)
 Neutron
•

Pea size sample
•
•

•
•

star

Weighs 100 million tons
Same density as an atomic nucleus

Strong magnetic field
First one discovered in early 1970s
•
•

Pulsar (pulsating radio source)
Found in the Crab nebula (remnant of an A.D.
1054 supernova)

Crab Nebula in the
constellation Taurus

Figure 24.14

24.2 Stellar remnants (continued)
 Black
•
•

•

More dense than a neutron star
Intense surface gravity lets no light escape
As matter is pulled into it
•
•

•

hole

Becomes very hot
Emits x-rays

Likely candidate is Cygnus X-1, a strong xray source

Quiz Break

24.3 Galaxies
 Milky
•

Way galaxy

Structure
•
•

•
•

Determined by using radio telescopes
Large spiral galaxy
• About 100,000 light-years wide
• Thickness at the galactic nucleus is about
10,000 light-years
Three spiral arms of stars
Sun is 30,000 light-years from the center

Face-on view of the
Milk Way Galaxy

Figure 24.18 A

Edge-on view of the
Milk Way Galaxy

Figure 24.18 B

24.3 Galaxies (continued)
 Milky
•

Rotation
•
•
•

•

Way galaxy

Around the galactic nucleus
Outermost stars move the slowest
Sun rotates around the galactic nucleus once
about every 200 million years

Halo surrounds the galactic disk
•
•
•

Spherical
Very tenuous gas
Numerous globular clusters

24.3 Galaxies (continued)
 Other
•
•

galaxies

Existence was first proposed in mid-1700s
by Immanuel Kant
Four basic types of galaxies
•

Spiral galaxy
• Arms extending from nucleus
• About 30% of all galaxies
• Large diameter of 20,000 to 125,000 light
years
• Contains both young and old stars
• e.g., Milky Way

Great Galaxy, a spiral galaxy, in
the constellation Andromeda

Figure 24.20

24.3 Galaxies (continued)
 Other
•

galaxies

Four basic types of galaxies
•

•

Barred spiral galaxy
• Stars arranged in the shape of a bar
• Generally quite large
• About 10% of all galaxies
Elliptical galaxy
• Ellipsoidal shape
• About 60% of all galaxies
• Most are smaller than spiral galaxies;
however, they are also the largest known
galaxies

A barred spiral galaxy

Figure 24.22

24.3 Galaxies (continued)
 Other
•

galaxies

Four basic types of galaxies
•

Irregular galaxy
• Lacks symmetry
• About 10% of all galaxies
• Contains mostly young stars
• e.g., Magellanic Clouds

24.3 Galaxies (continued)
 Galactic
•
•
•

Group of galaxies
Some contain thousands of galaxies
Local Group
•
•

•

cluster

Our own group of galaxies
Contains at least 28 galaxies

Supercluster
•
•

Huge swarm of galaxies
May be the largest entity in the universe

Quiz Break

24.4 Red shifts
 Doppler
•

effect

Change in the wavelength of light emitted
by an object due to its motion
•

•

Movement away stretches the wavelength
• Longer wavelength
• Light appears redder
Movement toward “squeezes” the wavelength
• Shorter wavelength
• Light shifted toward the blue

24.4 Red shifts (continued)
 Doppler
•

effect

Amount of the Doppler shift indicates the
rate of movement
•
•

Large Doppler shift indicates a high velocity
Small Doppler shift indicates a lower velocity

 Expanding
•

universe

Most galaxies exhibit a red Doppler shift
•

Moving away

Raisin bread analogy of an
expanding universe

Figure 24.24

24.4 Red shifts (continued)
 Expanding
•

universe

Most galaxies exhibit a red Doppler shift
•

•
•
•

Far galaxies
• Exhibit the greatest shift
• Greater velocity
Discovered in 1929 by Edwin Hubble
Hubble's Law – the recessional speed of
galaxies is proportional to their distance
Accounts for red shifts

24.4 Big Bang theory
 Accounts

for galaxies moving away

from us
 Universe was once confined to a "ball"
that was
•
•

•

Supermassive
Dense
Hot

24.4 Big Bang theory (continued)
 Big

Bang marks the inception of the
universe
•
•

Occurred about 15 billion years ago
All matter and space was created

 Matter

is moving outward
 Fate of the universe
•

Two possibilities
•
•

Universe will last forever
Outward expansion sill stop and gravitational;
contraction will follow

24.4 Big Bang theory (continued)
 Fate
•

of the universe

Final fate depends on the average density
of the universe
•
•

If the density is more than the critical density,
then the universe would contract
Current estimates point to less then the critical
density and predict an ever-expanding, or
open, universe

Chapter 24Test Guidance
You will be responsible on the test for answering 3 of the following 6
questions.
1.

2.

3.
4.
5.
6.

What causes the difference between a star’s apparent
magnitude and it absolute magnitude.
List and explain the three factors that control the apparent
brightness of a star as seen from Earth.
Describe how binary stars are used to determine stellar mass.
List and describe the four basic types of galaxies.
What is Hubble’s Law, please explain in detail.
Briefly describe the Big Bang Theory (not the TV show).

End of Chapter 24


Slide 55

Lecture Outlines
PowerPoint

Chapter 24
Earth Science 11e
Tarbuck/Lutgens
Modified for educational
purposes only
By S. Koziol 12-8-2010

© 2006 Pearson Prentice Hall

Earth Science, 11e
Beyond Our
Solar System
Chapter 24

24.1 Properties of stars
 Distance
•
•

Measuring a star's distance can be very
difficult
Stellar parallax
•
•
•

•
•

Used for measuring distance to a star
Apparent shift in a star's position due to the
orbital motion of Earth
Measured as an angle
Near stars have the largest parallax
Largest parallax is less than one second of arc

24. 1 Properties of stars
(continued)

 Distance
•
•

Distances to the stars are very large
Units of measurement
•
•

•

Kilometers or astronomical units are too
cumbersome to use
Light-year is used most often
• Distance that light travels in 1 year
• One light-year is 9.5 trillion km (5.8 trillion
miles)

Other methods for measuring distance are
also used

24. 1 Properties of stars
(continued)

 Stellar
•

Controlled by three factors
•

•
•

•

brightness

Size
Temperature
Distance

Magnitude
•

Measure of a star's brightness

24.1 Properties of stars
(continued)

 Stellar
•

brightness

Magnitude
•

Two types of measurement
• Apparent magnitude
• Brightness when a star is viewed from
Earth
• Decreases with distance
• Numbers are used to designate
magnitudes - dim stars have large
numbers and negative numbers are also
used

24.1 Properties of stars
(continued)

 Stellar
•

brightness

Magnitude
•

Two types of measurement
• Absolute magnitude
• "True" or intrinsic brightness of a star
• Brightness at a standard distance of
32.6 light-years
• Most stars' absolute magnitudes are
between -5 and +15

24.1 Properties of stars
(continued)

 Color
•

Hot star
•

•
•

•

and temperature

Temperature above 30,000 K
Emits short-wavelength light
Appears blue

Cool star
•
•
•

Temperature less than 3000 K
Emits longer-wavelength light
Appears red

24.1 Properties of stars
(continued)

 Color
•

and temperature

Between 5000 and 6000 K
•
•

Stars appear yellow
e.g., Sun

 Binary
•

stars and stellar mass

Binary stars
•

Two stars orbiting one another
• Stars are held together by mutual
gravitation
• Both orbit around a common center of mass

24.1 Properties of stars (continued)
 Binary
•

Binary stars
•

•
•

•

stars and stellar mass

Visual binaries are resolved telescopically
More than 50% of the stars in the universe are
binary stars
Used to determine stellar mass

Stellar mass
•

Determined using binary stars – the center of
mass is closest to the most massive star

Binary stars
orbit each
other around
their common
center of
mass
Figure 24.4

24.1 Properties of stars (continued)
 Binary
•

stars and stellar mass

Stellar mass
•

Mass of most stars is between one-tenth and
fifty times the mass of the Sun

24.1 Hertzsprung-Russell
diagram
 Shows
•
•

the relation between stellar

Brightness (absolute magnitude) and
Temperature

 Diagram

is made by plotting (graphing)
each star's
•
•

Luminosity (brightness) and
Temperature

24.1 Hertzsprung-Russell
diagram (continued)
 Parts
•

Main-sequence stars
•

•
•

•

of an H-R diagram

90% of all stars
Band through the center of the H-R diagram
Sun is in the main-sequence

Giants (or red giants)
•
•
•

Very luminous
Large
Upper-right on the H-R diagram

24.1 Hertzsprung-Russell
diagram (continued)
 Parts
•

Giants (or red giants)
•

•

•

of an H-R diagram

Very large giants are called supergiants
Only a few percent of all stars

White dwarfs
•
•

•
•
•

Fainter than main-sequence stars
Small (approximate the size of Earth)
Lower-central area on the H-R diagram
Not all are white in color
Perhaps 10% of all stars

Idealized HertzsprungRussell diagram

Figure 24.5

Quiz Break

24.2 Variable stars
 Stars

that fluctuate in brightness
 Types of variable stars
•

Pulsating variables
•
•

•

Fluctuate regularly in brightness
Expand and contract in size

Eruptive variables
•
•
•

Explosive event
Sudden brightening
Called a nova

24.2 Interstellar matter
 Between

the stars is "the vacuum of

space"
 Nebula
•
•

Cloud of dust and gases
Two major types of nebulae
•

Bright nebula
• Glows if it close to a very hot star
• Two types of bright nebulae
• Emission nebula
• Reflection nebula

The Orion Nebula is a wellknown emission nebula

Figure 24.8

A faint blue reflection nebula in
the Pleiades star cluster

Figure 24.9

24.2 Interstellar matter (continued)
 Nebula
•

Two major types of nebulae
•

Dark nebula
• Not close to any bright star
• Appear dark
• Contains the material that forms stars and
planets

24.2 Stellar evolution
 Stars

exist because of gravity
 Two opposing forces in a star are
•
•

Gravity – contracts
Thermal nuclear energy – expands

 Stages
•

Birth
•

•
•
•
•

In dark, cool, interstellar clouds
Gravity contracts the cloud
Temperature rises
Radiates long-wavelength (red) light
Becomes a protostar

24.2 Stellar evolution (continued)
 Stages
•

Protostar
•
•
•

•
•
•
•

Gravitational contraction of gaseous cloud
continues
Core reaches 10 million K
Hydrogen nuclei fuse
• Become helium nuclei
• Process is called hydrogen burning
Energy is released
Outward pressure increases
Outward pressure balanced by gravity pulling in
Star becomes a stable main-sequence star

24.2 Stellar evolution (continued)
 Stages
•

Main-sequence stage
•

Stars age at different rates
• Massive stars use fuel faster and exist for
only a few million years
• Small stars use fuel slowly and exist for
perhaps hundreds of billions of years

•

90% of a star's life is in the main-sequence

24.2 Stellar evolution (continued)
 Stages
•

Red giant stage
•
•

•
•
•

Hydrogen burning migrates outward
Star's outer envelope expands
• Surface cools
• Surface becomes red
Core is collapsing as helium is converted to
carbon
Eventually all nuclear fuel is used
Gravity squeezes the star

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Low-mass star
• 0.5 solar mass
• Red giant collapses
• Becomes a white dwarf

24.2 Evolutionary stages of
low mass stars

Figure 24.12 A

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Medium-mass star
• Between 0.5 and 3 solar masses
• Red giant collapses
• Planetary nebula forms
• Becomes a white dwarf

24.2 Evolutionary stages of
medium mass stars

Figure 24.12 B

H-R diagram showing
stellar evolution

Figure 24.11

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Massive star
• Over 3 solar masses
• Short life span
• Terminates in a brilliant explosion called
a supernova
• Interior condenses
• May produce a hot, dense object that is
either a neutron star or a black hole

24.2 Evolutionary stages of
massive stars

Figure 24.12 C

24.2 Stellar remnants
 White
•
•

Small (some no larger than Earth)
Dense
•
•
•

•
•

dwarf

Can be more massive than the Sun
Spoonful weighs several tons
Atoms take up less space
• Electrons displaced inward
• Called degenerate matter

Hot surface
Cools to become a black dwarf

24.2 Stellar remnants (continued)
 Neutron
•

Forms from a more massive star
•
•

•
•

star

Star has more gravity
Squeezes itself smaller

Remnant of a supernova
Gravitational force collapses atoms
•
•

Electrons combine with protons to produce
neutrons
Small size

24.2 Stellar remnants (continued)
 Neutron
•

Pea size sample
•
•

•
•

star

Weighs 100 million tons
Same density as an atomic nucleus

Strong magnetic field
First one discovered in early 1970s
•
•

Pulsar (pulsating radio source)
Found in the Crab nebula (remnant of an A.D.
1054 supernova)

Crab Nebula in the
constellation Taurus

Figure 24.14

24.2 Stellar remnants (continued)
 Black
•
•

•

More dense than a neutron star
Intense surface gravity lets no light escape
As matter is pulled into it
•
•

•

hole

Becomes very hot
Emits x-rays

Likely candidate is Cygnus X-1, a strong xray source

Quiz Break

24.3 Galaxies
 Milky
•

Way galaxy

Structure
•
•

•
•

Determined by using radio telescopes
Large spiral galaxy
• About 100,000 light-years wide
• Thickness at the galactic nucleus is about
10,000 light-years
Three spiral arms of stars
Sun is 30,000 light-years from the center

Face-on view of the
Milk Way Galaxy

Figure 24.18 A

Edge-on view of the
Milk Way Galaxy

Figure 24.18 B

24.3 Galaxies (continued)
 Milky
•

Rotation
•
•
•

•

Way galaxy

Around the galactic nucleus
Outermost stars move the slowest
Sun rotates around the galactic nucleus once
about every 200 million years

Halo surrounds the galactic disk
•
•
•

Spherical
Very tenuous gas
Numerous globular clusters

24.3 Galaxies (continued)
 Other
•
•

galaxies

Existence was first proposed in mid-1700s
by Immanuel Kant
Four basic types of galaxies
•

Spiral galaxy
• Arms extending from nucleus
• About 30% of all galaxies
• Large diameter of 20,000 to 125,000 light
years
• Contains both young and old stars
• e.g., Milky Way

Great Galaxy, a spiral galaxy, in
the constellation Andromeda

Figure 24.20

24.3 Galaxies (continued)
 Other
•

galaxies

Four basic types of galaxies
•

•

Barred spiral galaxy
• Stars arranged in the shape of a bar
• Generally quite large
• About 10% of all galaxies
Elliptical galaxy
• Ellipsoidal shape
• About 60% of all galaxies
• Most are smaller than spiral galaxies;
however, they are also the largest known
galaxies

A barred spiral galaxy

Figure 24.22

24.3 Galaxies (continued)
 Other
•

galaxies

Four basic types of galaxies
•

Irregular galaxy
• Lacks symmetry
• About 10% of all galaxies
• Contains mostly young stars
• e.g., Magellanic Clouds

24.3 Galaxies (continued)
 Galactic
•
•
•

Group of galaxies
Some contain thousands of galaxies
Local Group
•
•

•

cluster

Our own group of galaxies
Contains at least 28 galaxies

Supercluster
•
•

Huge swarm of galaxies
May be the largest entity in the universe

Quiz Break

24.4 Red shifts
 Doppler
•

effect

Change in the wavelength of light emitted
by an object due to its motion
•

•

Movement away stretches the wavelength
• Longer wavelength
• Light appears redder
Movement toward “squeezes” the wavelength
• Shorter wavelength
• Light shifted toward the blue

24.4 Red shifts (continued)
 Doppler
•

effect

Amount of the Doppler shift indicates the
rate of movement
•
•

Large Doppler shift indicates a high velocity
Small Doppler shift indicates a lower velocity

 Expanding
•

universe

Most galaxies exhibit a red Doppler shift
•

Moving away

Raisin bread analogy of an
expanding universe

Figure 24.24

24.4 Red shifts (continued)
 Expanding
•

universe

Most galaxies exhibit a red Doppler shift
•

•
•
•

Far galaxies
• Exhibit the greatest shift
• Greater velocity
Discovered in 1929 by Edwin Hubble
Hubble's Law – the recessional speed of
galaxies is proportional to their distance
Accounts for red shifts

24.4 Big Bang theory
 Accounts

for galaxies moving away

from us
 Universe was once confined to a "ball"
that was
•
•

•

Supermassive
Dense
Hot

24.4 Big Bang theory (continued)
 Big

Bang marks the inception of the
universe
•
•

Occurred about 15 billion years ago
All matter and space was created

 Matter

is moving outward
 Fate of the universe
•

Two possibilities
•
•

Universe will last forever
Outward expansion sill stop and gravitational;
contraction will follow

24.4 Big Bang theory (continued)
 Fate
•

of the universe

Final fate depends on the average density
of the universe
•
•

If the density is more than the critical density,
then the universe would contract
Current estimates point to less then the critical
density and predict an ever-expanding, or
open, universe

Chapter 24Test Guidance
You will be responsible on the test for answering 3 of the following 6
questions.
1.

2.

3.
4.
5.
6.

What causes the difference between a star’s apparent
magnitude and it absolute magnitude.
List and explain the three factors that control the apparent
brightness of a star as seen from Earth.
Describe how binary stars are used to determine stellar mass.
List and describe the four basic types of galaxies.
What is Hubble’s Law, please explain in detail.
Briefly describe the Big Bang Theory (not the TV show).

End of Chapter 24


Slide 56

Lecture Outlines
PowerPoint

Chapter 24
Earth Science 11e
Tarbuck/Lutgens
Modified for educational
purposes only
By S. Koziol 12-8-2010

© 2006 Pearson Prentice Hall

Earth Science, 11e
Beyond Our
Solar System
Chapter 24

24.1 Properties of stars
 Distance
•
•

Measuring a star's distance can be very
difficult
Stellar parallax
•
•
•

•
•

Used for measuring distance to a star
Apparent shift in a star's position due to the
orbital motion of Earth
Measured as an angle
Near stars have the largest parallax
Largest parallax is less than one second of arc

24. 1 Properties of stars
(continued)

 Distance
•
•

Distances to the stars are very large
Units of measurement
•
•

•

Kilometers or astronomical units are too
cumbersome to use
Light-year is used most often
• Distance that light travels in 1 year
• One light-year is 9.5 trillion km (5.8 trillion
miles)

Other methods for measuring distance are
also used

24. 1 Properties of stars
(continued)

 Stellar
•

Controlled by three factors
•

•
•

•

brightness

Size
Temperature
Distance

Magnitude
•

Measure of a star's brightness

24.1 Properties of stars
(continued)

 Stellar
•

brightness

Magnitude
•

Two types of measurement
• Apparent magnitude
• Brightness when a star is viewed from
Earth
• Decreases with distance
• Numbers are used to designate
magnitudes - dim stars have large
numbers and negative numbers are also
used

24.1 Properties of stars
(continued)

 Stellar
•

brightness

Magnitude
•

Two types of measurement
• Absolute magnitude
• "True" or intrinsic brightness of a star
• Brightness at a standard distance of
32.6 light-years
• Most stars' absolute magnitudes are
between -5 and +15

24.1 Properties of stars
(continued)

 Color
•

Hot star
•

•
•

•

and temperature

Temperature above 30,000 K
Emits short-wavelength light
Appears blue

Cool star
•
•
•

Temperature less than 3000 K
Emits longer-wavelength light
Appears red

24.1 Properties of stars
(continued)

 Color
•

and temperature

Between 5000 and 6000 K
•
•

Stars appear yellow
e.g., Sun

 Binary
•

stars and stellar mass

Binary stars
•

Two stars orbiting one another
• Stars are held together by mutual
gravitation
• Both orbit around a common center of mass

24.1 Properties of stars (continued)
 Binary
•

Binary stars
•

•
•

•

stars and stellar mass

Visual binaries are resolved telescopically
More than 50% of the stars in the universe are
binary stars
Used to determine stellar mass

Stellar mass
•

Determined using binary stars – the center of
mass is closest to the most massive star

Binary stars
orbit each
other around
their common
center of
mass
Figure 24.4

24.1 Properties of stars (continued)
 Binary
•

stars and stellar mass

Stellar mass
•

Mass of most stars is between one-tenth and
fifty times the mass of the Sun

24.1 Hertzsprung-Russell
diagram
 Shows
•
•

the relation between stellar

Brightness (absolute magnitude) and
Temperature

 Diagram

is made by plotting (graphing)
each star's
•
•

Luminosity (brightness) and
Temperature

24.1 Hertzsprung-Russell
diagram (continued)
 Parts
•

Main-sequence stars
•

•
•

•

of an H-R diagram

90% of all stars
Band through the center of the H-R diagram
Sun is in the main-sequence

Giants (or red giants)
•
•
•

Very luminous
Large
Upper-right on the H-R diagram

24.1 Hertzsprung-Russell
diagram (continued)
 Parts
•

Giants (or red giants)
•

•

•

of an H-R diagram

Very large giants are called supergiants
Only a few percent of all stars

White dwarfs
•
•

•
•
•

Fainter than main-sequence stars
Small (approximate the size of Earth)
Lower-central area on the H-R diagram
Not all are white in color
Perhaps 10% of all stars

Idealized HertzsprungRussell diagram

Figure 24.5

Quiz Break

24.2 Variable stars
 Stars

that fluctuate in brightness
 Types of variable stars
•

Pulsating variables
•
•

•

Fluctuate regularly in brightness
Expand and contract in size

Eruptive variables
•
•
•

Explosive event
Sudden brightening
Called a nova

24.2 Interstellar matter
 Between

the stars is "the vacuum of

space"
 Nebula
•
•

Cloud of dust and gases
Two major types of nebulae
•

Bright nebula
• Glows if it close to a very hot star
• Two types of bright nebulae
• Emission nebula
• Reflection nebula

The Orion Nebula is a wellknown emission nebula

Figure 24.8

A faint blue reflection nebula in
the Pleiades star cluster

Figure 24.9

24.2 Interstellar matter (continued)
 Nebula
•

Two major types of nebulae
•

Dark nebula
• Not close to any bright star
• Appear dark
• Contains the material that forms stars and
planets

24.2 Stellar evolution
 Stars

exist because of gravity
 Two opposing forces in a star are
•
•

Gravity – contracts
Thermal nuclear energy – expands

 Stages
•

Birth
•

•
•
•
•

In dark, cool, interstellar clouds
Gravity contracts the cloud
Temperature rises
Radiates long-wavelength (red) light
Becomes a protostar

24.2 Stellar evolution (continued)
 Stages
•

Protostar
•
•
•

•
•
•
•

Gravitational contraction of gaseous cloud
continues
Core reaches 10 million K
Hydrogen nuclei fuse
• Become helium nuclei
• Process is called hydrogen burning
Energy is released
Outward pressure increases
Outward pressure balanced by gravity pulling in
Star becomes a stable main-sequence star

24.2 Stellar evolution (continued)
 Stages
•

Main-sequence stage
•

Stars age at different rates
• Massive stars use fuel faster and exist for
only a few million years
• Small stars use fuel slowly and exist for
perhaps hundreds of billions of years

•

90% of a star's life is in the main-sequence

24.2 Stellar evolution (continued)
 Stages
•

Red giant stage
•
•

•
•
•

Hydrogen burning migrates outward
Star's outer envelope expands
• Surface cools
• Surface becomes red
Core is collapsing as helium is converted to
carbon
Eventually all nuclear fuel is used
Gravity squeezes the star

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Low-mass star
• 0.5 solar mass
• Red giant collapses
• Becomes a white dwarf

24.2 Evolutionary stages of
low mass stars

Figure 24.12 A

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Medium-mass star
• Between 0.5 and 3 solar masses
• Red giant collapses
• Planetary nebula forms
• Becomes a white dwarf

24.2 Evolutionary stages of
medium mass stars

Figure 24.12 B

H-R diagram showing
stellar evolution

Figure 24.11

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Massive star
• Over 3 solar masses
• Short life span
• Terminates in a brilliant explosion called
a supernova
• Interior condenses
• May produce a hot, dense object that is
either a neutron star or a black hole

24.2 Evolutionary stages of
massive stars

Figure 24.12 C

24.2 Stellar remnants
 White
•
•

Small (some no larger than Earth)
Dense
•
•
•

•
•

dwarf

Can be more massive than the Sun
Spoonful weighs several tons
Atoms take up less space
• Electrons displaced inward
• Called degenerate matter

Hot surface
Cools to become a black dwarf

24.2 Stellar remnants (continued)
 Neutron
•

Forms from a more massive star
•
•

•
•

star

Star has more gravity
Squeezes itself smaller

Remnant of a supernova
Gravitational force collapses atoms
•
•

Electrons combine with protons to produce
neutrons
Small size

24.2 Stellar remnants (continued)
 Neutron
•

Pea size sample
•
•

•
•

star

Weighs 100 million tons
Same density as an atomic nucleus

Strong magnetic field
First one discovered in early 1970s
•
•

Pulsar (pulsating radio source)
Found in the Crab nebula (remnant of an A.D.
1054 supernova)

Crab Nebula in the
constellation Taurus

Figure 24.14

24.2 Stellar remnants (continued)
 Black
•
•

•

More dense than a neutron star
Intense surface gravity lets no light escape
As matter is pulled into it
•
•

•

hole

Becomes very hot
Emits x-rays

Likely candidate is Cygnus X-1, a strong xray source

Quiz Break

24.3 Galaxies
 Milky
•

Way galaxy

Structure
•
•

•
•

Determined by using radio telescopes
Large spiral galaxy
• About 100,000 light-years wide
• Thickness at the galactic nucleus is about
10,000 light-years
Three spiral arms of stars
Sun is 30,000 light-years from the center

Face-on view of the
Milk Way Galaxy

Figure 24.18 A

Edge-on view of the
Milk Way Galaxy

Figure 24.18 B

24.3 Galaxies (continued)
 Milky
•

Rotation
•
•
•

•

Way galaxy

Around the galactic nucleus
Outermost stars move the slowest
Sun rotates around the galactic nucleus once
about every 200 million years

Halo surrounds the galactic disk
•
•
•

Spherical
Very tenuous gas
Numerous globular clusters

24.3 Galaxies (continued)
 Other
•
•

galaxies

Existence was first proposed in mid-1700s
by Immanuel Kant
Four basic types of galaxies
•

Spiral galaxy
• Arms extending from nucleus
• About 30% of all galaxies
• Large diameter of 20,000 to 125,000 light
years
• Contains both young and old stars
• e.g., Milky Way

Great Galaxy, a spiral galaxy, in
the constellation Andromeda

Figure 24.20

24.3 Galaxies (continued)
 Other
•

galaxies

Four basic types of galaxies
•

•

Barred spiral galaxy
• Stars arranged in the shape of a bar
• Generally quite large
• About 10% of all galaxies
Elliptical galaxy
• Ellipsoidal shape
• About 60% of all galaxies
• Most are smaller than spiral galaxies;
however, they are also the largest known
galaxies

A barred spiral galaxy

Figure 24.22

24.3 Galaxies (continued)
 Other
•

galaxies

Four basic types of galaxies
•

Irregular galaxy
• Lacks symmetry
• About 10% of all galaxies
• Contains mostly young stars
• e.g., Magellanic Clouds

24.3 Galaxies (continued)
 Galactic
•
•
•

Group of galaxies
Some contain thousands of galaxies
Local Group
•
•

•

cluster

Our own group of galaxies
Contains at least 28 galaxies

Supercluster
•
•

Huge swarm of galaxies
May be the largest entity in the universe

Quiz Break

24.4 Red shifts
 Doppler
•

effect

Change in the wavelength of light emitted
by an object due to its motion
•

•

Movement away stretches the wavelength
• Longer wavelength
• Light appears redder
Movement toward “squeezes” the wavelength
• Shorter wavelength
• Light shifted toward the blue

24.4 Red shifts (continued)
 Doppler
•

effect

Amount of the Doppler shift indicates the
rate of movement
•
•

Large Doppler shift indicates a high velocity
Small Doppler shift indicates a lower velocity

 Expanding
•

universe

Most galaxies exhibit a red Doppler shift
•

Moving away

Raisin bread analogy of an
expanding universe

Figure 24.24

24.4 Red shifts (continued)
 Expanding
•

universe

Most galaxies exhibit a red Doppler shift
•

•
•
•

Far galaxies
• Exhibit the greatest shift
• Greater velocity
Discovered in 1929 by Edwin Hubble
Hubble's Law – the recessional speed of
galaxies is proportional to their distance
Accounts for red shifts

24.4 Big Bang theory
 Accounts

for galaxies moving away

from us
 Universe was once confined to a "ball"
that was
•
•

•

Supermassive
Dense
Hot

24.4 Big Bang theory (continued)
 Big

Bang marks the inception of the
universe
•
•

Occurred about 15 billion years ago
All matter and space was created

 Matter

is moving outward
 Fate of the universe
•

Two possibilities
•
•

Universe will last forever
Outward expansion sill stop and gravitational;
contraction will follow

24.4 Big Bang theory (continued)
 Fate
•

of the universe

Final fate depends on the average density
of the universe
•
•

If the density is more than the critical density,
then the universe would contract
Current estimates point to less then the critical
density and predict an ever-expanding, or
open, universe

Chapter 24Test Guidance
You will be responsible on the test for answering 3 of the following 6
questions.
1.

2.

3.
4.
5.
6.

What causes the difference between a star’s apparent
magnitude and it absolute magnitude.
List and explain the three factors that control the apparent
brightness of a star as seen from Earth.
Describe how binary stars are used to determine stellar mass.
List and describe the four basic types of galaxies.
What is Hubble’s Law, please explain in detail.
Briefly describe the Big Bang Theory (not the TV show).

End of Chapter 24


Slide 57

Lecture Outlines
PowerPoint

Chapter 24
Earth Science 11e
Tarbuck/Lutgens
Modified for educational
purposes only
By S. Koziol 12-8-2010

© 2006 Pearson Prentice Hall

Earth Science, 11e
Beyond Our
Solar System
Chapter 24

24.1 Properties of stars
 Distance
•
•

Measuring a star's distance can be very
difficult
Stellar parallax
•
•
•

•
•

Used for measuring distance to a star
Apparent shift in a star's position due to the
orbital motion of Earth
Measured as an angle
Near stars have the largest parallax
Largest parallax is less than one second of arc

24. 1 Properties of stars
(continued)

 Distance
•
•

Distances to the stars are very large
Units of measurement
•
•

•

Kilometers or astronomical units are too
cumbersome to use
Light-year is used most often
• Distance that light travels in 1 year
• One light-year is 9.5 trillion km (5.8 trillion
miles)

Other methods for measuring distance are
also used

24. 1 Properties of stars
(continued)

 Stellar
•

Controlled by three factors
•

•
•

•

brightness

Size
Temperature
Distance

Magnitude
•

Measure of a star's brightness

24.1 Properties of stars
(continued)

 Stellar
•

brightness

Magnitude
•

Two types of measurement
• Apparent magnitude
• Brightness when a star is viewed from
Earth
• Decreases with distance
• Numbers are used to designate
magnitudes - dim stars have large
numbers and negative numbers are also
used

24.1 Properties of stars
(continued)

 Stellar
•

brightness

Magnitude
•

Two types of measurement
• Absolute magnitude
• "True" or intrinsic brightness of a star
• Brightness at a standard distance of
32.6 light-years
• Most stars' absolute magnitudes are
between -5 and +15

24.1 Properties of stars
(continued)

 Color
•

Hot star
•

•
•

•

and temperature

Temperature above 30,000 K
Emits short-wavelength light
Appears blue

Cool star
•
•
•

Temperature less than 3000 K
Emits longer-wavelength light
Appears red

24.1 Properties of stars
(continued)

 Color
•

and temperature

Between 5000 and 6000 K
•
•

Stars appear yellow
e.g., Sun

 Binary
•

stars and stellar mass

Binary stars
•

Two stars orbiting one another
• Stars are held together by mutual
gravitation
• Both orbit around a common center of mass

24.1 Properties of stars (continued)
 Binary
•

Binary stars
•

•
•

•

stars and stellar mass

Visual binaries are resolved telescopically
More than 50% of the stars in the universe are
binary stars
Used to determine stellar mass

Stellar mass
•

Determined using binary stars – the center of
mass is closest to the most massive star

Binary stars
orbit each
other around
their common
center of
mass
Figure 24.4

24.1 Properties of stars (continued)
 Binary
•

stars and stellar mass

Stellar mass
•

Mass of most stars is between one-tenth and
fifty times the mass of the Sun

24.1 Hertzsprung-Russell
diagram
 Shows
•
•

the relation between stellar

Brightness (absolute magnitude) and
Temperature

 Diagram

is made by plotting (graphing)
each star's
•
•

Luminosity (brightness) and
Temperature

24.1 Hertzsprung-Russell
diagram (continued)
 Parts
•

Main-sequence stars
•

•
•

•

of an H-R diagram

90% of all stars
Band through the center of the H-R diagram
Sun is in the main-sequence

Giants (or red giants)
•
•
•

Very luminous
Large
Upper-right on the H-R diagram

24.1 Hertzsprung-Russell
diagram (continued)
 Parts
•

Giants (or red giants)
•

•

•

of an H-R diagram

Very large giants are called supergiants
Only a few percent of all stars

White dwarfs
•
•

•
•
•

Fainter than main-sequence stars
Small (approximate the size of Earth)
Lower-central area on the H-R diagram
Not all are white in color
Perhaps 10% of all stars

Idealized HertzsprungRussell diagram

Figure 24.5

Quiz Break

24.2 Variable stars
 Stars

that fluctuate in brightness
 Types of variable stars
•

Pulsating variables
•
•

•

Fluctuate regularly in brightness
Expand and contract in size

Eruptive variables
•
•
•

Explosive event
Sudden brightening
Called a nova

24.2 Interstellar matter
 Between

the stars is "the vacuum of

space"
 Nebula
•
•

Cloud of dust and gases
Two major types of nebulae
•

Bright nebula
• Glows if it close to a very hot star
• Two types of bright nebulae
• Emission nebula
• Reflection nebula

The Orion Nebula is a wellknown emission nebula

Figure 24.8

A faint blue reflection nebula in
the Pleiades star cluster

Figure 24.9

24.2 Interstellar matter (continued)
 Nebula
•

Two major types of nebulae
•

Dark nebula
• Not close to any bright star
• Appear dark
• Contains the material that forms stars and
planets

24.2 Stellar evolution
 Stars

exist because of gravity
 Two opposing forces in a star are
•
•

Gravity – contracts
Thermal nuclear energy – expands

 Stages
•

Birth
•

•
•
•
•

In dark, cool, interstellar clouds
Gravity contracts the cloud
Temperature rises
Radiates long-wavelength (red) light
Becomes a protostar

24.2 Stellar evolution (continued)
 Stages
•

Protostar
•
•
•

•
•
•
•

Gravitational contraction of gaseous cloud
continues
Core reaches 10 million K
Hydrogen nuclei fuse
• Become helium nuclei
• Process is called hydrogen burning
Energy is released
Outward pressure increases
Outward pressure balanced by gravity pulling in
Star becomes a stable main-sequence star

24.2 Stellar evolution (continued)
 Stages
•

Main-sequence stage
•

Stars age at different rates
• Massive stars use fuel faster and exist for
only a few million years
• Small stars use fuel slowly and exist for
perhaps hundreds of billions of years

•

90% of a star's life is in the main-sequence

24.2 Stellar evolution (continued)
 Stages
•

Red giant stage
•
•

•
•
•

Hydrogen burning migrates outward
Star's outer envelope expands
• Surface cools
• Surface becomes red
Core is collapsing as helium is converted to
carbon
Eventually all nuclear fuel is used
Gravity squeezes the star

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Low-mass star
• 0.5 solar mass
• Red giant collapses
• Becomes a white dwarf

24.2 Evolutionary stages of
low mass stars

Figure 24.12 A

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Medium-mass star
• Between 0.5 and 3 solar masses
• Red giant collapses
• Planetary nebula forms
• Becomes a white dwarf

24.2 Evolutionary stages of
medium mass stars

Figure 24.12 B

H-R diagram showing
stellar evolution

Figure 24.11

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Massive star
• Over 3 solar masses
• Short life span
• Terminates in a brilliant explosion called
a supernova
• Interior condenses
• May produce a hot, dense object that is
either a neutron star or a black hole

24.2 Evolutionary stages of
massive stars

Figure 24.12 C

24.2 Stellar remnants
 White
•
•

Small (some no larger than Earth)
Dense
•
•
•

•
•

dwarf

Can be more massive than the Sun
Spoonful weighs several tons
Atoms take up less space
• Electrons displaced inward
• Called degenerate matter

Hot surface
Cools to become a black dwarf

24.2 Stellar remnants (continued)
 Neutron
•

Forms from a more massive star
•
•

•
•

star

Star has more gravity
Squeezes itself smaller

Remnant of a supernova
Gravitational force collapses atoms
•
•

Electrons combine with protons to produce
neutrons
Small size

24.2 Stellar remnants (continued)
 Neutron
•

Pea size sample
•
•

•
•

star

Weighs 100 million tons
Same density as an atomic nucleus

Strong magnetic field
First one discovered in early 1970s
•
•

Pulsar (pulsating radio source)
Found in the Crab nebula (remnant of an A.D.
1054 supernova)

Crab Nebula in the
constellation Taurus

Figure 24.14

24.2 Stellar remnants (continued)
 Black
•
•

•

More dense than a neutron star
Intense surface gravity lets no light escape
As matter is pulled into it
•
•

•

hole

Becomes very hot
Emits x-rays

Likely candidate is Cygnus X-1, a strong xray source

Quiz Break

24.3 Galaxies
 Milky
•

Way galaxy

Structure
•
•

•
•

Determined by using radio telescopes
Large spiral galaxy
• About 100,000 light-years wide
• Thickness at the galactic nucleus is about
10,000 light-years
Three spiral arms of stars
Sun is 30,000 light-years from the center

Face-on view of the
Milk Way Galaxy

Figure 24.18 A

Edge-on view of the
Milk Way Galaxy

Figure 24.18 B

24.3 Galaxies (continued)
 Milky
•

Rotation
•
•
•

•

Way galaxy

Around the galactic nucleus
Outermost stars move the slowest
Sun rotates around the galactic nucleus once
about every 200 million years

Halo surrounds the galactic disk
•
•
•

Spherical
Very tenuous gas
Numerous globular clusters

24.3 Galaxies (continued)
 Other
•
•

galaxies

Existence was first proposed in mid-1700s
by Immanuel Kant
Four basic types of galaxies
•

Spiral galaxy
• Arms extending from nucleus
• About 30% of all galaxies
• Large diameter of 20,000 to 125,000 light
years
• Contains both young and old stars
• e.g., Milky Way

Great Galaxy, a spiral galaxy, in
the constellation Andromeda

Figure 24.20

24.3 Galaxies (continued)
 Other
•

galaxies

Four basic types of galaxies
•

•

Barred spiral galaxy
• Stars arranged in the shape of a bar
• Generally quite large
• About 10% of all galaxies
Elliptical galaxy
• Ellipsoidal shape
• About 60% of all galaxies
• Most are smaller than spiral galaxies;
however, they are also the largest known
galaxies

A barred spiral galaxy

Figure 24.22

24.3 Galaxies (continued)
 Other
•

galaxies

Four basic types of galaxies
•

Irregular galaxy
• Lacks symmetry
• About 10% of all galaxies
• Contains mostly young stars
• e.g., Magellanic Clouds

24.3 Galaxies (continued)
 Galactic
•
•
•

Group of galaxies
Some contain thousands of galaxies
Local Group
•
•

•

cluster

Our own group of galaxies
Contains at least 28 galaxies

Supercluster
•
•

Huge swarm of galaxies
May be the largest entity in the universe

Quiz Break

24.4 Red shifts
 Doppler
•

effect

Change in the wavelength of light emitted
by an object due to its motion
•

•

Movement away stretches the wavelength
• Longer wavelength
• Light appears redder
Movement toward “squeezes” the wavelength
• Shorter wavelength
• Light shifted toward the blue

24.4 Red shifts (continued)
 Doppler
•

effect

Amount of the Doppler shift indicates the
rate of movement
•
•

Large Doppler shift indicates a high velocity
Small Doppler shift indicates a lower velocity

 Expanding
•

universe

Most galaxies exhibit a red Doppler shift
•

Moving away

Raisin bread analogy of an
expanding universe

Figure 24.24

24.4 Red shifts (continued)
 Expanding
•

universe

Most galaxies exhibit a red Doppler shift
•

•
•
•

Far galaxies
• Exhibit the greatest shift
• Greater velocity
Discovered in 1929 by Edwin Hubble
Hubble's Law – the recessional speed of
galaxies is proportional to their distance
Accounts for red shifts

24.4 Big Bang theory
 Accounts

for galaxies moving away

from us
 Universe was once confined to a "ball"
that was
•
•

•

Supermassive
Dense
Hot

24.4 Big Bang theory (continued)
 Big

Bang marks the inception of the
universe
•
•

Occurred about 15 billion years ago
All matter and space was created

 Matter

is moving outward
 Fate of the universe
•

Two possibilities
•
•

Universe will last forever
Outward expansion sill stop and gravitational;
contraction will follow

24.4 Big Bang theory (continued)
 Fate
•

of the universe

Final fate depends on the average density
of the universe
•
•

If the density is more than the critical density,
then the universe would contract
Current estimates point to less then the critical
density and predict an ever-expanding, or
open, universe

Chapter 24Test Guidance
You will be responsible on the test for answering 3 of the following 6
questions.
1.

2.

3.
4.
5.
6.

What causes the difference between a star’s apparent
magnitude and it absolute magnitude.
List and explain the three factors that control the apparent
brightness of a star as seen from Earth.
Describe how binary stars are used to determine stellar mass.
List and describe the four basic types of galaxies.
What is Hubble’s Law, please explain in detail.
Briefly describe the Big Bang Theory (not the TV show).

End of Chapter 24


Slide 58

Lecture Outlines
PowerPoint

Chapter 24
Earth Science 11e
Tarbuck/Lutgens
Modified for educational
purposes only
By S. Koziol 12-8-2010

© 2006 Pearson Prentice Hall

Earth Science, 11e
Beyond Our
Solar System
Chapter 24

24.1 Properties of stars
 Distance
•
•

Measuring a star's distance can be very
difficult
Stellar parallax
•
•
•

•
•

Used for measuring distance to a star
Apparent shift in a star's position due to the
orbital motion of Earth
Measured as an angle
Near stars have the largest parallax
Largest parallax is less than one second of arc

24. 1 Properties of stars
(continued)

 Distance
•
•

Distances to the stars are very large
Units of measurement
•
•

•

Kilometers or astronomical units are too
cumbersome to use
Light-year is used most often
• Distance that light travels in 1 year
• One light-year is 9.5 trillion km (5.8 trillion
miles)

Other methods for measuring distance are
also used

24. 1 Properties of stars
(continued)

 Stellar
•

Controlled by three factors
•

•
•

•

brightness

Size
Temperature
Distance

Magnitude
•

Measure of a star's brightness

24.1 Properties of stars
(continued)

 Stellar
•

brightness

Magnitude
•

Two types of measurement
• Apparent magnitude
• Brightness when a star is viewed from
Earth
• Decreases with distance
• Numbers are used to designate
magnitudes - dim stars have large
numbers and negative numbers are also
used

24.1 Properties of stars
(continued)

 Stellar
•

brightness

Magnitude
•

Two types of measurement
• Absolute magnitude
• "True" or intrinsic brightness of a star
• Brightness at a standard distance of
32.6 light-years
• Most stars' absolute magnitudes are
between -5 and +15

24.1 Properties of stars
(continued)

 Color
•

Hot star
•

•
•

•

and temperature

Temperature above 30,000 K
Emits short-wavelength light
Appears blue

Cool star
•
•
•

Temperature less than 3000 K
Emits longer-wavelength light
Appears red

24.1 Properties of stars
(continued)

 Color
•

and temperature

Between 5000 and 6000 K
•
•

Stars appear yellow
e.g., Sun

 Binary
•

stars and stellar mass

Binary stars
•

Two stars orbiting one another
• Stars are held together by mutual
gravitation
• Both orbit around a common center of mass

24.1 Properties of stars (continued)
 Binary
•

Binary stars
•

•
•

•

stars and stellar mass

Visual binaries are resolved telescopically
More than 50% of the stars in the universe are
binary stars
Used to determine stellar mass

Stellar mass
•

Determined using binary stars – the center of
mass is closest to the most massive star

Binary stars
orbit each
other around
their common
center of
mass
Figure 24.4

24.1 Properties of stars (continued)
 Binary
•

stars and stellar mass

Stellar mass
•

Mass of most stars is between one-tenth and
fifty times the mass of the Sun

24.1 Hertzsprung-Russell
diagram
 Shows
•
•

the relation between stellar

Brightness (absolute magnitude) and
Temperature

 Diagram

is made by plotting (graphing)
each star's
•
•

Luminosity (brightness) and
Temperature

24.1 Hertzsprung-Russell
diagram (continued)
 Parts
•

Main-sequence stars
•

•
•

•

of an H-R diagram

90% of all stars
Band through the center of the H-R diagram
Sun is in the main-sequence

Giants (or red giants)
•
•
•

Very luminous
Large
Upper-right on the H-R diagram

24.1 Hertzsprung-Russell
diagram (continued)
 Parts
•

Giants (or red giants)
•

•

•

of an H-R diagram

Very large giants are called supergiants
Only a few percent of all stars

White dwarfs
•
•

•
•
•

Fainter than main-sequence stars
Small (approximate the size of Earth)
Lower-central area on the H-R diagram
Not all are white in color
Perhaps 10% of all stars

Idealized HertzsprungRussell diagram

Figure 24.5

Quiz Break

24.2 Variable stars
 Stars

that fluctuate in brightness
 Types of variable stars
•

Pulsating variables
•
•

•

Fluctuate regularly in brightness
Expand and contract in size

Eruptive variables
•
•
•

Explosive event
Sudden brightening
Called a nova

24.2 Interstellar matter
 Between

the stars is "the vacuum of

space"
 Nebula
•
•

Cloud of dust and gases
Two major types of nebulae
•

Bright nebula
• Glows if it close to a very hot star
• Two types of bright nebulae
• Emission nebula
• Reflection nebula

The Orion Nebula is a wellknown emission nebula

Figure 24.8

A faint blue reflection nebula in
the Pleiades star cluster

Figure 24.9

24.2 Interstellar matter (continued)
 Nebula
•

Two major types of nebulae
•

Dark nebula
• Not close to any bright star
• Appear dark
• Contains the material that forms stars and
planets

24.2 Stellar evolution
 Stars

exist because of gravity
 Two opposing forces in a star are
•
•

Gravity – contracts
Thermal nuclear energy – expands

 Stages
•

Birth
•

•
•
•
•

In dark, cool, interstellar clouds
Gravity contracts the cloud
Temperature rises
Radiates long-wavelength (red) light
Becomes a protostar

24.2 Stellar evolution (continued)
 Stages
•

Protostar
•
•
•

•
•
•
•

Gravitational contraction of gaseous cloud
continues
Core reaches 10 million K
Hydrogen nuclei fuse
• Become helium nuclei
• Process is called hydrogen burning
Energy is released
Outward pressure increases
Outward pressure balanced by gravity pulling in
Star becomes a stable main-sequence star

24.2 Stellar evolution (continued)
 Stages
•

Main-sequence stage
•

Stars age at different rates
• Massive stars use fuel faster and exist for
only a few million years
• Small stars use fuel slowly and exist for
perhaps hundreds of billions of years

•

90% of a star's life is in the main-sequence

24.2 Stellar evolution (continued)
 Stages
•

Red giant stage
•
•

•
•
•

Hydrogen burning migrates outward
Star's outer envelope expands
• Surface cools
• Surface becomes red
Core is collapsing as helium is converted to
carbon
Eventually all nuclear fuel is used
Gravity squeezes the star

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Low-mass star
• 0.5 solar mass
• Red giant collapses
• Becomes a white dwarf

24.2 Evolutionary stages of
low mass stars

Figure 24.12 A

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Medium-mass star
• Between 0.5 and 3 solar masses
• Red giant collapses
• Planetary nebula forms
• Becomes a white dwarf

24.2 Evolutionary stages of
medium mass stars

Figure 24.12 B

H-R diagram showing
stellar evolution

Figure 24.11

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Massive star
• Over 3 solar masses
• Short life span
• Terminates in a brilliant explosion called
a supernova
• Interior condenses
• May produce a hot, dense object that is
either a neutron star or a black hole

24.2 Evolutionary stages of
massive stars

Figure 24.12 C

24.2 Stellar remnants
 White
•
•

Small (some no larger than Earth)
Dense
•
•
•

•
•

dwarf

Can be more massive than the Sun
Spoonful weighs several tons
Atoms take up less space
• Electrons displaced inward
• Called degenerate matter

Hot surface
Cools to become a black dwarf

24.2 Stellar remnants (continued)
 Neutron
•

Forms from a more massive star
•
•

•
•

star

Star has more gravity
Squeezes itself smaller

Remnant of a supernova
Gravitational force collapses atoms
•
•

Electrons combine with protons to produce
neutrons
Small size

24.2 Stellar remnants (continued)
 Neutron
•

Pea size sample
•
•

•
•

star

Weighs 100 million tons
Same density as an atomic nucleus

Strong magnetic field
First one discovered in early 1970s
•
•

Pulsar (pulsating radio source)
Found in the Crab nebula (remnant of an A.D.
1054 supernova)

Crab Nebula in the
constellation Taurus

Figure 24.14

24.2 Stellar remnants (continued)
 Black
•
•

•

More dense than a neutron star
Intense surface gravity lets no light escape
As matter is pulled into it
•
•

•

hole

Becomes very hot
Emits x-rays

Likely candidate is Cygnus X-1, a strong xray source

Quiz Break

24.3 Galaxies
 Milky
•

Way galaxy

Structure
•
•

•
•

Determined by using radio telescopes
Large spiral galaxy
• About 100,000 light-years wide
• Thickness at the galactic nucleus is about
10,000 light-years
Three spiral arms of stars
Sun is 30,000 light-years from the center

Face-on view of the
Milk Way Galaxy

Figure 24.18 A

Edge-on view of the
Milk Way Galaxy

Figure 24.18 B

24.3 Galaxies (continued)
 Milky
•

Rotation
•
•
•

•

Way galaxy

Around the galactic nucleus
Outermost stars move the slowest
Sun rotates around the galactic nucleus once
about every 200 million years

Halo surrounds the galactic disk
•
•
•

Spherical
Very tenuous gas
Numerous globular clusters

24.3 Galaxies (continued)
 Other
•
•

galaxies

Existence was first proposed in mid-1700s
by Immanuel Kant
Four basic types of galaxies
•

Spiral galaxy
• Arms extending from nucleus
• About 30% of all galaxies
• Large diameter of 20,000 to 125,000 light
years
• Contains both young and old stars
• e.g., Milky Way

Great Galaxy, a spiral galaxy, in
the constellation Andromeda

Figure 24.20

24.3 Galaxies (continued)
 Other
•

galaxies

Four basic types of galaxies
•

•

Barred spiral galaxy
• Stars arranged in the shape of a bar
• Generally quite large
• About 10% of all galaxies
Elliptical galaxy
• Ellipsoidal shape
• About 60% of all galaxies
• Most are smaller than spiral galaxies;
however, they are also the largest known
galaxies

A barred spiral galaxy

Figure 24.22

24.3 Galaxies (continued)
 Other
•

galaxies

Four basic types of galaxies
•

Irregular galaxy
• Lacks symmetry
• About 10% of all galaxies
• Contains mostly young stars
• e.g., Magellanic Clouds

24.3 Galaxies (continued)
 Galactic
•
•
•

Group of galaxies
Some contain thousands of galaxies
Local Group
•
•

•

cluster

Our own group of galaxies
Contains at least 28 galaxies

Supercluster
•
•

Huge swarm of galaxies
May be the largest entity in the universe

Quiz Break

24.4 Red shifts
 Doppler
•

effect

Change in the wavelength of light emitted
by an object due to its motion
•

•

Movement away stretches the wavelength
• Longer wavelength
• Light appears redder
Movement toward “squeezes” the wavelength
• Shorter wavelength
• Light shifted toward the blue

24.4 Red shifts (continued)
 Doppler
•

effect

Amount of the Doppler shift indicates the
rate of movement
•
•

Large Doppler shift indicates a high velocity
Small Doppler shift indicates a lower velocity

 Expanding
•

universe

Most galaxies exhibit a red Doppler shift
•

Moving away

Raisin bread analogy of an
expanding universe

Figure 24.24

24.4 Red shifts (continued)
 Expanding
•

universe

Most galaxies exhibit a red Doppler shift
•

•
•
•

Far galaxies
• Exhibit the greatest shift
• Greater velocity
Discovered in 1929 by Edwin Hubble
Hubble's Law – the recessional speed of
galaxies is proportional to their distance
Accounts for red shifts

24.4 Big Bang theory
 Accounts

for galaxies moving away

from us
 Universe was once confined to a "ball"
that was
•
•

•

Supermassive
Dense
Hot

24.4 Big Bang theory (continued)
 Big

Bang marks the inception of the
universe
•
•

Occurred about 15 billion years ago
All matter and space was created

 Matter

is moving outward
 Fate of the universe
•

Two possibilities
•
•

Universe will last forever
Outward expansion sill stop and gravitational;
contraction will follow

24.4 Big Bang theory (continued)
 Fate
•

of the universe

Final fate depends on the average density
of the universe
•
•

If the density is more than the critical density,
then the universe would contract
Current estimates point to less then the critical
density and predict an ever-expanding, or
open, universe

Chapter 24Test Guidance
You will be responsible on the test for answering 3 of the following 6
questions.
1.

2.

3.
4.
5.
6.

What causes the difference between a star’s apparent
magnitude and it absolute magnitude.
List and explain the three factors that control the apparent
brightness of a star as seen from Earth.
Describe how binary stars are used to determine stellar mass.
List and describe the four basic types of galaxies.
What is Hubble’s Law, please explain in detail.
Briefly describe the Big Bang Theory (not the TV show).

End of Chapter 24


Slide 59

Lecture Outlines
PowerPoint

Chapter 24
Earth Science 11e
Tarbuck/Lutgens
Modified for educational
purposes only
By S. Koziol 12-8-2010

© 2006 Pearson Prentice Hall

Earth Science, 11e
Beyond Our
Solar System
Chapter 24

24.1 Properties of stars
 Distance
•
•

Measuring a star's distance can be very
difficult
Stellar parallax
•
•
•

•
•

Used for measuring distance to a star
Apparent shift in a star's position due to the
orbital motion of Earth
Measured as an angle
Near stars have the largest parallax
Largest parallax is less than one second of arc

24. 1 Properties of stars
(continued)

 Distance
•
•

Distances to the stars are very large
Units of measurement
•
•

•

Kilometers or astronomical units are too
cumbersome to use
Light-year is used most often
• Distance that light travels in 1 year
• One light-year is 9.5 trillion km (5.8 trillion
miles)

Other methods for measuring distance are
also used

24. 1 Properties of stars
(continued)

 Stellar
•

Controlled by three factors
•

•
•

•

brightness

Size
Temperature
Distance

Magnitude
•

Measure of a star's brightness

24.1 Properties of stars
(continued)

 Stellar
•

brightness

Magnitude
•

Two types of measurement
• Apparent magnitude
• Brightness when a star is viewed from
Earth
• Decreases with distance
• Numbers are used to designate
magnitudes - dim stars have large
numbers and negative numbers are also
used

24.1 Properties of stars
(continued)

 Stellar
•

brightness

Magnitude
•

Two types of measurement
• Absolute magnitude
• "True" or intrinsic brightness of a star
• Brightness at a standard distance of
32.6 light-years
• Most stars' absolute magnitudes are
between -5 and +15

24.1 Properties of stars
(continued)

 Color
•

Hot star
•

•
•

•

and temperature

Temperature above 30,000 K
Emits short-wavelength light
Appears blue

Cool star
•
•
•

Temperature less than 3000 K
Emits longer-wavelength light
Appears red

24.1 Properties of stars
(continued)

 Color
•

and temperature

Between 5000 and 6000 K
•
•

Stars appear yellow
e.g., Sun

 Binary
•

stars and stellar mass

Binary stars
•

Two stars orbiting one another
• Stars are held together by mutual
gravitation
• Both orbit around a common center of mass

24.1 Properties of stars (continued)
 Binary
•

Binary stars
•

•
•

•

stars and stellar mass

Visual binaries are resolved telescopically
More than 50% of the stars in the universe are
binary stars
Used to determine stellar mass

Stellar mass
•

Determined using binary stars – the center of
mass is closest to the most massive star

Binary stars
orbit each
other around
their common
center of
mass
Figure 24.4

24.1 Properties of stars (continued)
 Binary
•

stars and stellar mass

Stellar mass
•

Mass of most stars is between one-tenth and
fifty times the mass of the Sun

24.1 Hertzsprung-Russell
diagram
 Shows
•
•

the relation between stellar

Brightness (absolute magnitude) and
Temperature

 Diagram

is made by plotting (graphing)
each star's
•
•

Luminosity (brightness) and
Temperature

24.1 Hertzsprung-Russell
diagram (continued)
 Parts
•

Main-sequence stars
•

•
•

•

of an H-R diagram

90% of all stars
Band through the center of the H-R diagram
Sun is in the main-sequence

Giants (or red giants)
•
•
•

Very luminous
Large
Upper-right on the H-R diagram

24.1 Hertzsprung-Russell
diagram (continued)
 Parts
•

Giants (or red giants)
•

•

•

of an H-R diagram

Very large giants are called supergiants
Only a few percent of all stars

White dwarfs
•
•

•
•
•

Fainter than main-sequence stars
Small (approximate the size of Earth)
Lower-central area on the H-R diagram
Not all are white in color
Perhaps 10% of all stars

Idealized HertzsprungRussell diagram

Figure 24.5

Quiz Break

24.2 Variable stars
 Stars

that fluctuate in brightness
 Types of variable stars
•

Pulsating variables
•
•

•

Fluctuate regularly in brightness
Expand and contract in size

Eruptive variables
•
•
•

Explosive event
Sudden brightening
Called a nova

24.2 Interstellar matter
 Between

the stars is "the vacuum of

space"
 Nebula
•
•

Cloud of dust and gases
Two major types of nebulae
•

Bright nebula
• Glows if it close to a very hot star
• Two types of bright nebulae
• Emission nebula
• Reflection nebula

The Orion Nebula is a wellknown emission nebula

Figure 24.8

A faint blue reflection nebula in
the Pleiades star cluster

Figure 24.9

24.2 Interstellar matter (continued)
 Nebula
•

Two major types of nebulae
•

Dark nebula
• Not close to any bright star
• Appear dark
• Contains the material that forms stars and
planets

24.2 Stellar evolution
 Stars

exist because of gravity
 Two opposing forces in a star are
•
•

Gravity – contracts
Thermal nuclear energy – expands

 Stages
•

Birth
•

•
•
•
•

In dark, cool, interstellar clouds
Gravity contracts the cloud
Temperature rises
Radiates long-wavelength (red) light
Becomes a protostar

24.2 Stellar evolution (continued)
 Stages
•

Protostar
•
•
•

•
•
•
•

Gravitational contraction of gaseous cloud
continues
Core reaches 10 million K
Hydrogen nuclei fuse
• Become helium nuclei
• Process is called hydrogen burning
Energy is released
Outward pressure increases
Outward pressure balanced by gravity pulling in
Star becomes a stable main-sequence star

24.2 Stellar evolution (continued)
 Stages
•

Main-sequence stage
•

Stars age at different rates
• Massive stars use fuel faster and exist for
only a few million years
• Small stars use fuel slowly and exist for
perhaps hundreds of billions of years

•

90% of a star's life is in the main-sequence

24.2 Stellar evolution (continued)
 Stages
•

Red giant stage
•
•

•
•
•

Hydrogen burning migrates outward
Star's outer envelope expands
• Surface cools
• Surface becomes red
Core is collapsing as helium is converted to
carbon
Eventually all nuclear fuel is used
Gravity squeezes the star

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Low-mass star
• 0.5 solar mass
• Red giant collapses
• Becomes a white dwarf

24.2 Evolutionary stages of
low mass stars

Figure 24.12 A

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Medium-mass star
• Between 0.5 and 3 solar masses
• Red giant collapses
• Planetary nebula forms
• Becomes a white dwarf

24.2 Evolutionary stages of
medium mass stars

Figure 24.12 B

H-R diagram showing
stellar evolution

Figure 24.11

24.2 Stellar evolution (continued)
 Stages
•

Burnout and death
•
•

Final stage depends on mass
Possibilities
• Massive star
• Over 3 solar masses
• Short life span
• Terminates in a brilliant explosion called
a supernova
• Interior condenses
• May produce a hot, dense object that is
either a neutron star or a black hole

24.2 Evolutionary stages of
massive stars

Figure 24.12 C

24.2 Stellar remnants
 White
•
•

Small (some no larger than Earth)
Dense
•
•
•

•
•

dwarf

Can be more massive than the Sun
Spoonful weighs several tons
Atoms take up less space
• Electrons displaced inward
• Called degenerate matter

Hot surface
Cools to become a black dwarf

24.2 Stellar remnants (continued)
 Neutron
•

Forms from a more massive star
•
•

•
•

star

Star has more gravity
Squeezes itself smaller

Remnant of a supernova
Gravitational force collapses atoms
•
•

Electrons combine with protons to produce
neutrons
Small size

24.2 Stellar remnants (continued)
 Neutron
•

Pea size sample
•
•

•
•

star

Weighs 100 million tons
Same density as an atomic nucleus

Strong magnetic field
First one discovered in early 1970s
•
•

Pulsar (pulsating radio source)
Found in the Crab nebula (remnant of an A.D.
1054 supernova)

Crab Nebula in the
constellation Taurus

Figure 24.14

24.2 Stellar remnants (continued)
 Black
•
•

•

More dense than a neutron star
Intense surface gravity lets no light escape
As matter is pulled into it
•
•

•

hole

Becomes very hot
Emits x-rays

Likely candidate is Cygnus X-1, a strong xray source

Quiz Break

24.3 Galaxies
 Milky
•

Way galaxy

Structure
•
•

•
•

Determined by using radio telescopes
Large spiral galaxy
• About 100,000 light-years wide
• Thickness at the galactic nucleus is about
10,000 light-years
Three spiral arms of stars
Sun is 30,000 light-years from the center

Face-on view of the
Milk Way Galaxy

Figure 24.18 A

Edge-on view of the
Milk Way Galaxy

Figure 24.18 B

24.3 Galaxies (continued)
 Milky
•

Rotation
•
•
•

•

Way galaxy

Around the galactic nucleus
Outermost stars move the slowest
Sun rotates around the galactic nucleus once
about every 200 million years

Halo surrounds the galactic disk
•
•
•

Spherical
Very tenuous gas
Numerous globular clusters

24.3 Galaxies (continued)
 Other
•
•

galaxies

Existence was first proposed in mid-1700s
by Immanuel Kant
Four basic types of galaxies
•

Spiral galaxy
• Arms extending from nucleus
• About 30% of all galaxies
• Large diameter of 20,000 to 125,000 light
years
• Contains both young and old stars
• e.g., Milky Way

Great Galaxy, a spiral galaxy, in
the constellation Andromeda

Figure 24.20

24.3 Galaxies (continued)
 Other
•

galaxies

Four basic types of galaxies
•

•

Barred spiral galaxy
• Stars arranged in the shape of a bar
• Generally quite large
• About 10% of all galaxies
Elliptical galaxy
• Ellipsoidal shape
• About 60% of all galaxies
• Most are smaller than spiral galaxies;
however, they are also the largest known
galaxies

A barred spiral galaxy

Figure 24.22

24.3 Galaxies (continued)
 Other
•

galaxies

Four basic types of galaxies
•

Irregular galaxy
• Lacks symmetry
• About 10% of all galaxies
• Contains mostly young stars
• e.g., Magellanic Clouds

24.3 Galaxies (continued)
 Galactic
•
•
•

Group of galaxies
Some contain thousands of galaxies
Local Group
•
•

•

cluster

Our own group of galaxies
Contains at least 28 galaxies

Supercluster
•
•

Huge swarm of galaxies
May be the largest entity in the universe

Quiz Break

24.4 Red shifts
 Doppler
•

effect

Change in the wavelength of light emitted
by an object due to its motion
•

•

Movement away stretches the wavelength
• Longer wavelength
• Light appears redder
Movement toward “squeezes” the wavelength
• Shorter wavelength
• Light shifted toward the blue

24.4 Red shifts (continued)
 Doppler
•

effect

Amount of the Doppler shift indicates the
rate of movement
•
•

Large Doppler shift indicates a high velocity
Small Doppler shift indicates a lower velocity

 Expanding
•

universe

Most galaxies exhibit a red Doppler shift
•

Moving away

Raisin bread analogy of an
expanding universe

Figure 24.24

24.4 Red shifts (continued)
 Expanding
•

universe

Most galaxies exhibit a red Doppler shift
•

•
•
•

Far galaxies
• Exhibit the greatest shift
• Greater velocity
Discovered in 1929 by Edwin Hubble
Hubble's Law – the recessional speed of
galaxies is proportional to their distance
Accounts for red shifts

24.4 Big Bang theory
 Accounts

for galaxies moving away

from us
 Universe was once confined to a "ball"
that was
•
•

•

Supermassive
Dense
Hot

24.4 Big Bang theory (continued)
 Big

Bang marks the inception of the
universe
•
•

Occurred about 15 billion years ago
All matter and space was created

 Matter

is moving outward
 Fate of the universe
•

Two possibilities
•
•

Universe will last forever
Outward expansion sill stop and gravitational;
contraction will follow

24.4 Big Bang theory (continued)
 Fate
•

of the universe

Final fate depends on the average density
of the universe
•
•

If the density is more than the critical density,
then the universe would contract
Current estimates point to less then the critical
density and predict an ever-expanding, or
open, universe

Chapter 24Test Guidance
You will be responsible on the test for answering 3 of the following 6
questions.
1.

2.

3.
4.
5.
6.

What causes the difference between a star’s apparent
magnitude and it absolute magnitude.
List and explain the three factors that control the apparent
brightness of a star as seen from Earth.
Describe how binary stars are used to determine stellar mass.
List and describe the four basic types of galaxies.
What is Hubble’s Law, please explain in detail.
Briefly describe the Big Bang Theory (not the TV show).

End of Chapter 24