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Milky way
- The galaxy that includes the solar system; appears as a hazy white band in the night sky
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Galaxy
- a huge collection of stars, planets, gas, and dust that is 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 to 1000 stars; open clusters appear along the band of the milky way
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globular cluster
- a collection of 100000 to 1 million stars that is arranged in a distinctive spherical shape; globular clusters are around the center of the milky way
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local group
- a small group of about 40 galaxies that include the milky way
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super cluster
- a gigantic cluster of 4 to 25 clusters of galaxies that is hundreds of million of light years in size
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shapes of galaxies
- the galaxies are either spiral (which means it looks like a pinwheel), elliptical (which means it looks like an ellipsoid) or irregular which doesn't follow any of these rules
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cosmology
- the study of the universe
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doppler effect
- the change in pitch of a sound due to the motion of the source relative to an observer; also the change in frequency of a light source due to is 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 of the visible spectrum
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blueshift
- the effect in which objects moving towards an observer have their wavelengths shortened, toward the blue end of the spectrum
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big bang
- the event that may have triggered the expansion of the universe 14 billion years ago
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CMB
- the radiation left over from the big bang, which fills the universe
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Dark matter
- the most abundant form of matter in the universe; invisible to telescopes
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Dark energy
- a form of energy that makes up nearly 3 quarters of the universe; has the effect of increasing the expansion of the universe
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