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6 Cards in this Set
- Front
- Back
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Planets
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Small, spherical, nonluminous bodies that orbit a star and shine by reflected light.
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What is a star?
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A self-luminous ball of hot gas that generates its own energy
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Astronomical unit (AU)=
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The average distance from the Earth to the sun. 1.5e+11
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1 light-year (ly)=
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The distance that light travels in one year. 10^3 or 63,000 AU.
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What is a galaxy?
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A great cloud of stars, gas, and dust bound together by the combined gravity of all matter.
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What are the spiral arms of a galaxy?
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Great clouds of gas and dust where stars are formed.
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