Download 2010–2015 Edusmart Answer Key for The Universe

Answer Key for The Universe
Note-taking Guide
The Universe Defined
universe,
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space
The universe is everything that exists. That includes everything from our planet Earth to
the deep space that stretches endlessly outwards.
The universe is gigantic. No one really knows how big it is. But this gigantic, mysterious
universe isn't just empty space.
Stars
Brighter,
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Most of the universe is made up of stars, galaxies, gas, and dust.
Stars are enormous balls of gases. They are made up of mostly hydrogen and helium.
Nuclear reactions convert the hydrogen into helium. These reactions give off energy in
the form of light and heat. The Sun also gives out heat and light that makes life on Earth
possible. In fact, the Sun is a medium-sized star.
The properties that scientists use to classify and study stars include color, temperature,
size, and brightness.
Color tells us a lot about temperature, or how hot an object is.
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Each color signifies a different temperature range.
A star’s brightness, or luminosity, depends on how far away it is from Earth and how
much energy it puts out in a given time.
From Earth, the Sun appears brighter than any other star because it is thousands of
times closer to us than any other star.
A star's luminosity also depends on the star's size.
The bigger star will shine more brightly or be more luminous.
Stars and the H-R Diagram
nebula,
brightness,
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Stars start off as clouds of gas and dust, called a nebula.
Gravity pulls this gas and dust together until it forms a dense sphere.
The hydrogen starts changing to helium followed by an explosion and a main sequence
star is formed.
What happens to a star next depends on its mass. A star that is of average mass, like
our Sun, will expand into a red giant.
This stage will last until it collapses and all that will remain is a white dwarf star.
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Stars that are much bigger than the Sun will expand into red supergiants and eventually
explode into a supernova. Sometimes they'll form a dense neutron star or a black hole.
The gravitational force of a black hole is so great that even light can’t escape it.
To classify stars, scientists use the Hertzsprung-Russell diagram.
This diagram shows how stars are classified by their temperature and brightness.
Stars are plotted along the H-R diagram according to temperature and luminosity.
The star located near the middle of the H-R diagram is our Sun and we use it to
compare other stars against.
Stars found along the diagonal band from the top left to the bottom right in an H-R
Diagram are main sequence stars.
Galaxies
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A galaxy is made of billions of stars clustered together.
Gravity pulls stars, gas, and dust together to form galaxies.
Scientists classify galaxies according to their shape.
A galaxy that is circular or egg-shaped is called an elliptical galaxy
The largest types of galaxies are usually elliptical and very old.
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super clusters,
gravity,
young,
Most of the galaxies in the universe are shaped like our Milky Way galaxy. These are
called spiral galaxies.
Spiral-shaped galaxies have a thick bulge in the center and spiral arms that coil
outwards, like a pinwheel. New stars form in these spiral arms.
Our Sun and the solar system are found on the edge of one of the spiral arms of the
Milky Way galaxy.
When a galaxy does not have a specific shape, it's known as an irregular galaxy. It is full
of gas, dust, and young stars.
Galaxies do not stand alone in space. They group together in clusters. Sometimes, a
cluster of galaxies form larger groups called super clusters.
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