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Milky Way
The galaxy that includes the solar system; appears as hazy white band in the night sky
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Galaxy
a huge collection of stars, planets, gas, and dust, held together by gravity
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Star cluster
a collection of stars held together by gravity
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Open cluster
a collection of 50-1000 star; open clusters appear along the main band of the Milky Way
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Globular cluster
A collection of 100 000 to a million stars that is arranged in a distinct spherical shape, globular clusters are around the center of the Milky Way
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Local group
The small group of about 40 galaxies that includes the Milky Way
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Supercluster
a gigantic cluster of 4 to 25 clusters of galaxZies that is hundreds of millions of light-years in size
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Shapes of galaxies
- Spiral
- a type of galaxy that looks like a pinwheel when viewed from above and has a bulge when looking on it's side
- Elliptical
- A type of galaxy that ranges in shape from a perfect sphere to a stretched out ellipse. They contain some of the oldest stars in the universe
- Irregular
- A galaxy that has an irregular shape and can be made up of old and new stars.
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Cosmology
The study of the universe
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Doppler effect
The change in pitch due to the motion of the source relative to an observer. It is also the change in frequency of a light source due to it's motion relative to an observer
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Redshift
The effect in which objects moving away from an observer have their wavelengths lengthened, toward the red end if the visible spectrum
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Blueshift
The effect in which objects moving toward an observer have their wavelengths shortened
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Big bang
The event that may have triggered the expansion of the universe 14 years
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Cosmic microwave background (CMB)
The radiation left over from the big bang, which fills the universe
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Dark matter
The most abundant form of energy in the universe, is not visible to telescope
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Dark energy
A form of energy that makes nearly three quarters of the universe (73%); has the effect of increasing the expansion of the universe
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