Transcript Stars, Galaxies, and the Universe Section 1 Tools of Modern Astronomy  Constellations: Patterns of stars in the sky.

Stars, Galaxies, and the
Universe
Section 1
Tools of Modern Astronomy
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Constellations: Patterns of stars in the
sky.
Electromagnetic Radiation
Visible light: Light you see with your eyes.
 Electromagnetic radiation: Energy that
can travel directly through space in the
form of waves.
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Electromagnetic Spectrum
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Wavelength: The distance
between the crest of one
wave and the crest of the
next wave.
Spectrum: light that spreads
out to make a range of
different colors with different
wavelengths.
Electromagnetic spectrum:
includes radio waves,
infrared radiation, visible
light, ultraviolet radiation, Xrays, and gamma rays.
Telescopes
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Telescopes: Collect and focus different types of
electromagnetic radiation including visible light.
Convex lens: A piece of transparent glass, curved so
that the middle is thicker than the edges.
Refracting telescopes: use convex lens to gather a large
amount of light and focus it into a small area.
Reflecting telescopes: Uses a mirror instead of a lens.
Radio Telescopes: Detect radio waves from objects in
space.
Observatory: A building that contains one or more
telescopes.
Spectrographs
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Spectrograph: Breaks the light from an object
into colors and photographs the resulting
spectrum.
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Astronomers use spectrographs to get
information about stars, including their chemical
compositions and temperatures.
Chemical Composition and
Temperature of Stars
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Chemical elements in a star’s atmosphere
absorb light from the star. Each element absorbs
light at different wavelengths. Thus by
comparing them to other known spectrums of
different elements astronomers can infer which
elements are found in a star.
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Chemical composition of stars are about 73%
hydrogen,25% helium, and 2% other elements.
By comparing a star’s spectrum with the known
spectrums of elements at different temperatures,
astronomers can infer how hot the star is.
Review
For what purpose are telescopes designed?
Telescopes collect and focus electromagnet
radiation.
What can astronomers tell from looking at a
star’s spectrum?
Astronomers can determine the chemical
composition and the temperature of the star.
Section 2
Characteristics of Stars
Terms
Characteristics of Stars
Galaxy: Contains hundreds of billions of
stars. (Milky Way)
 Universe: All of space and everything in
it.
 Light-year: Distance that light travels in
one year. It is a unit of distance not time.
 Parallax: The apparent change in position
of an object when you look at it from
different places.
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Classifying Stars
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The main
characteristics used to
classify stars are:
Size, Temperature
and Brightness.
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Star sizes largest to
smallest are:
Super Giant, Giant,
Medium, White
Dwarf, and Neutron
stars.
Color and Temperature of Stars
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A stars color reveals its temperature. The
coolest stars are red and hottest stars are blue,
blue-white.
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The brightness of a star depends upon its size
and temperature.
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How bright a star looks from Earth depends on
both how far the star is from Earth and how
bright the star actually is.
Brightness
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Apparent magnitude: Is the star’s
brightness as seen from Earth. (use
electronic devices to measure it.
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Absolute magnitude: A brightness a star
would have if it were a standard distance
from Earth.
Hertzsprung-Russell Diagram
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A graph used by
astronomers that shows
the relationship between
surface temperature and
brightness of stars.
Most stars (90%) fall under
the Main Sequence in
which surface
temperatures increases as
brightness increases.
Review
What is a parallax? How is it useful in astronomy?
Parallax is the apparent change in an object’s position
when viewed from two different places. Astronomers
can use parallax to calculate distances to nearby
stars.
 List three characteristics used to classify stars.
Size, temperature (or color) and brightness
Which is hotter-- a red star or a blue star? Why?
Blue stars are hotter than red stars because gas glows
red at lower temperatures and blue at higher
temperatures.
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Section 3
Lives of Stars
A Star Is Born
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Nebula: All stars start out as nebulas. A large
amount of gas and dust spread out in an
immense volume.
Proto: Greek for “earliest”
Protostar: Earliest stage of a star.
A star is born when the contrasting gas and dust
become so hot that nuclear fusion starts.
How long a star lives depends on how much
mass it has. (More mass=shorter lives)
Death of Stars
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When a star runs out of
fuel, it becomes a white
dwarf, a neutron star, or
a black hole.
When it runs out of fuel
the center of the star
shrinks and the outer
part of the star
expands.
Terms of Stars
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White dwarf: The remaining hot core of a star after its
outer layers have expanded and drifted out into space.
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Neutron Star: A tiny star that remains after a supernova
explosion.
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Supernova: The explosion of a dying giant or
supergiant star.
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Black hole: The remains of an extremely massive star
pulled into a small volume by the force of gravity.
Review
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What is the earliest stage in the life of a star?
The star begins as part of a nebula. A cloud of dust and
gas. Some of the dust and gas condenses to form a
protostar. Nuclear fusion begins and the protostar
becomes a star.
Why do small-mass stars have longer lifetimes than
large-mass stars?
Small-mass stars burn their fuel more slowly than largemass stars.
Review continued
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What is the difference between stars that
become white dwarfs and stars that become
neutron stars?
Giant stars collapse into neutron stars. Smaller
stars form white dwarfs.
What evidence do astronomers use to detect
black holes?
Scientist detect black holes by observing
radiation from hot gas near the black hole, and
by studying the effect of the black hole’s gravity
on a nearby star.
Section 4
Star Systems and Galaxies
Star Systems and Planets
Our solar system has only one star, the
sun.
 More than half of all stars are members of
groups of two or more stars, called star
systems.
 Binary Stars: Star systems with two stars
are called double stars or binary stars.
 Eclipsing Binary: A System in which one
star blocks the light from another.
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Review
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What was the Big Bang?
A giant explosion in which all the matter in the universe began
moving apart.
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Describe how the solar system formed.
The solar system formed out of a collapsing, spinning disk of gas
and dust. The center of the disk formed the sun. Matter toward the
edge formed the planets, asteroids, and a cloud of ice and other
substances.
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What observations show that the universe is expanding?
The galaxies are all moving away from each other. The farther away
a galaxy is away from the Milky Way, the faster it moves away,
because there is more space.
Galaxies
3 Main Galaxies: Spiral Galaxies,
Elliptical Galaxies
Irregular Galaxies
Spiral: A galaxy that has the shape of twin
spirals.
Elliptical: Look like flatten balls.
Irregular: Do not have a regular shape.
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Review
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What is a star system?
A star system is a group of two or more stars.
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Describe the 3 main types of galaxies.
Spiral galaxies are shaped like twin spirals, with arms that
spiral out like pinwheels. Elliptical galaxies look like flattened
balls. Irregular galaxies do not have regular shapes.
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Where is the sun in our galaxy?
The sun is about 25,000 light-years away from the center of
the galaxy, about 2/3 of the way out in one of the spiral arms.
Section 5
History of the Universe
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The galaxies in the universe are like the raisins
in rising bread. The raisins move away from
each other as the bread rises.
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The universe is getting bigger all the time.
Big Bang Theory
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The initial explosion
that resulted in the
formation and
expansion of the
universe.
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The universe was
small, hot, and
dense. It exploded
about 10 to 15 billion
years ago to make
our universe.
Formation of the Solar System
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After the big bang, matter in the universe separated into
galaxies. Gas and dust spread throughout space in our
galaxy. About 5 billion years ago, a giant cloud of gas
and dust, or nebula, collapsed to form the solar system.
Nebula shrank to form a disk = the sun was born.
The spheres closest to the sun lost most of their gases
and became the inner planets.
The spheres farthest from the sun became the gas
giants or the outer planets.