Transcript Ch. 5 The Universe and Solar System

Ch. 5 The Universe and Solar
System
Pg 124-147
Origin and Structure of the Universe
• The Universe Defined
– The universe consists of all the matter, energy, and
space that have existed since the beginning of
time.
– Most of the distance between stars is empty
space.
– Universe consists of empty space, stars, planets,
satellites, asteroids, comets, & meteoroids.
– Interstellar gas & dust, H & atomic particles.
Galaxies
• Galaxies are clusters of stars and stars and
galaxies aren’t evenly distributed in space.
• 3 Types of Galaxies:
– Spiral: shaped like a flat disk or pinwheel with a
bright, bulging central core.
– Elliptical: shaped like an ellipse or sphere.
– Irregular: oddly shaped and resembles an
explosion frozen in time.
Spiral Galaxies
• Central core contains older stars.
• Spiral arms radiate outward from center and
wrap around the galaxy.
• Arms contain numerous young stars and
interstellar gas and dust.
• Shape comes from their rotation.
Elliptical Galaxies
• Contains older stars and lacks the interstellar
gas and dust needed for new star
development.
• Most large galaxies are spiral galaxies but,
elliptical galaxies seem to be more numerous.
Irregular Galaxies
• Contain a large amount of interstellar gas and
dust which indicates young star development.
• Only a small percentage of all known galaxies
are irregular galaxies.
The Milky Way Galaxy
• 1780 Sir William Herschel was able to use
observations and calculations to show that the
Earth and the Sun are located in a disk shaped
group of stars called a galaxy.
• Our galaxy is the Milky Way galaxy and it is a
spiral shaped galaxy.
• We reside in an arm of our galaxy and the
bright band in the sky is the galaxy itself.
Distances in Space
• AU—astronomical unit: 150,000,000km; the
distance between our planet and the sun.
• Light year—LY: 41,000,000,000,000km or 41
trillion km.
– A light year is the distance light travels in 1 year,
about 9.46 trillion km.
– The nearest star is 4.3 light years away.
Origin of the Universe: The Big Bang
Theory
• Scientists think that nearly 15 billion years ago
the universe was created.
• Think it was an explosive event which
produced all the matter and energy in the
universe.
• We call it the Big Bang Theory and there’s a lot
of evidence to support this but there still are
unanswered questions and unknown details.
Big Bang Theory
• Suggests that all matter and energy that exist
today in the universe was concentrated in a
very small dense object.
• For some reason it began to expand, creating
time and space.
• Lighter elements formed, followed by heavier
elements and stars began to evolve.
Big Bang Theory
• Proof: 1929 Edwin Hubble observed that galaxies
are moving away from each other—that the
universe is expanding.
• Red shift—means movement is away.
• Proof 2: 1965 Arno Penzlas and Robert Wilson
discovered background radiation—a remnant of
the Big Bang. It is evenly distributed.
• Proof 3: 1995 NASA discovered deuterium (heavy
isotope of H) scattered throughout the universe.
Alternative Theory: The Oscillating
Universe
• Some scientists think the universe will not
continue to expand indefinitely.
• Expansion will be reversed by the gravitational
attraction of all the matter in the universe.
• This is the pulsating or oscillation universe
theory.
• Weak evidence in support of this theory.
Another Alternative Theory: The
Steady State Universe
• Steady State Universe Theory was proposed in
the late 1940s.
• Suggests that the universe is unchanging and
never had a beginning and will never have an
ending.
• New matter is created to fill voids in space and
to maintain a consistent density of galaxies.
• Ruined in 1965—Background radiation as
proof of the Big Bang Theory.
Classification of Stars
• Stars vary in color due to the wavelength of
light they give off.
• Red light = cool stars.
• Blue light = hot stars.
• Stars vary in brightness, or magnitude.
– Apparent magnitude is how bright a star appears
to be when seen from the Earth.
– Absolute magnitude is how bright the star really
is.
Classification of Stars
• Apparent magnitude is a function of the star’s
absolute magnitude and its distance from the
Earth.
• Ex: faint star looks bright because it is close to
the Earth.
• Ex: brighter star looks faint because it is so
much farther away from the Earth than the
faint star in the 1st example.
Classification of Stars
• Ejnar Hertzsprung and Henry Norris Russell
recognized the relationship between the
absolute magnitude and the temperature of
stars by plotting the data from many stars on a
graph.
• This graph is the Hertzsprung-Russell Diagram
or H-R Diagram.
• It shows that stars fall into groups related to
their temperature and brightness.
Classification of Stars
• Main sequence: The majority of stars plot in
this band, ranging from cool dim stars to hot
bright stars.
• Giants: above the main sequence is this
cluster of bright cool stars.
• Supergiants: Above the giants is this cluster of
very bright cool stars.
• White dwarfs: Below the main sequence is
this group of hot dim stars.
Classification of Stars
• The H-R Diagram suggests that all stars pass
through a series of stages in their life cycles.
Classification of Stars
• Life stages of a star:
– Gas & dust particles come together & compact.
– Increase in pressure & temperature by becoming
more dense & compact.
– Stars to emit radiation.
– If star is hot enough, nuclear fusion takes place
taking 4 H nuclei & releasing 1 He nucleus, 2
positrons, & energy.
– Star is stable.
Classification of Stars
• Life stages of a star:
– As energy is depleted, nuclear fusion stops and
the star collapses, generating lots of heat.
– The heat causes the star to rapidly expand and
becomes a red giant or supergiant star.
– It collapses and explodes, losing its outer layers.
– This flare up of a star is called a nova or
supernova.
– The dying star shrinks into a white dwarf and
becomes dull and cold.
Classification of Stars
• The length of a star’s life cycle depends on
how much gas and dust was present in the
initial cloud and on how massive the star
became.
Our Sun: An Average Star
• The Sun is a stable, average size yellow star in
the main sequence.
• Has a surface temperature of 5500°C.
• Largest object in our solar system—a million
Earths could fit inside it.
• Light takes 8 minutes and 20 seconds to reach
the Earth.
• Much of what we know about the Sun has
been learned by analyzing the light from it.
Our Sun: An Average Star
• Like other stars, complex processes in the sun
produce other elements.
• H & He combine to form other heavier atoms.
• Does this under high pressure and
temperature.
• More than 60 elements have been identified
in the sun’s gases.
• 75% of the sun’s mass is H, 24% is He, the rest
is made up of other elements.
Earth and Our Solar System
• Formation of the Solar System
– Scientists think the expanding clouds of dust & gas
from the Big Bang gradually condensed to form
galaxies filled w/stars.
– Our Sun began 5 billion years ago and accounts for
99% of all the matter in our solar system.
Earth’s Position in the Solar System
• Ptolemy: 150 AD, Egyptian astronomer
Ptolemy developed a Geocentric model of the
solar system.
• Copernicus: Early 1500s, Polish astronomer
Nicolaus Copernicus proposed a Heliocentric
model of the solar system.
– It explained and predicted the motion of the
planets better but, it wasn’t accepted at the time.
Earth’s Position in the Solar System
• Brahe: Late 1500s, Danish astronomer Tycho
Brahe built an observatory and made
observations and calculations on the
movement of the planets.
• Kepler: 1600, German astronomer Johannes
Kepler became Tycho’s assistant and used and
studied Tycho’s records to describe planetary
motion with mathematical laws.
Earth’s Position in the Solar System
• Galileo: 1609, Italian astronomer Galileo
Galilei built a telescope and was the 1st
scientist to study the sky.
• He discovered the 4 biggest moons of Jupiter
& the phases of Venus.
• He accepted Copernicus’s Heliocentric model
of the solar system but, it wasn’t accepted at
the time. (He was persecuted for this).
Gravity: A Universal Force
• Every object in the universe exerts a
gravitational pull on every other object.
• Trend: The greater the masses, the greater
the gravitational force and the farther apart
the objects, the weaker the gravitational
force.
• Gravity is responsible for the spherical shape
of large objects in the universe.
Placing a Satellite in Orbit
• Orbit: is the path of a body revolving around
another body.
• For a satellite to orbit the Earth, the forces
created by the satellite’s orbital speed and the
Earth’s gravitational pull must be in balance.
• Greater gravitational force of the Earth =
satellite will fall to the Earth; greater orbital
speed of the satellite = satellite will go into
orbit higher above the Earth.
Kepler’s 3 Laws of Planetary Motion—
Early 1600s
• 1. The Law of Ellipses. The orbit of each
planet is an ellipse.
• 2. The Law of Areas. An imaginary line
connecting a planet to the sun sweeps out
equal areas in equal amounts of time.
• 3. The Harmonic Law. p^2 = d^3; where p is
the period of revolution in years and d is the
distance from the sun in AUs. (pg 144-math).
Orbits within Our Solar System
• All objects that revolve around the sun are
influenced by the sun’s gravitational pull.
• Orbits of planets, asteroids, comets, and etc.
are elliptical.
• Perihelion: is an object’s closest point to the
sun. January for the Earth.
• Aphelion: is an object’s farthest point from
the sun. July for the Earth.
Orbits within Our Solar System
• Most asteroids are located between the orbits
of Mars and Jupiter and have orbits similar to
the planets.
• Asteroids have elongated orbits that take
them from a position close to the sun to a
position beyond Jupiter’s orbit.
• The orbits of comets are the most elongated.