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15 Cards in this Set
- Front
- Back
astronomical unit
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a unit of measurement equal to the average distance between the Sun and Earth
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light-year
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a unit of measurement equal to the distance light travels in one year
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parsec
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a unit used in astronomy to describe large distance, such as the widths of galaxies
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nebula
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a cloud of gas and dust that was probably cast off from other stars that once were in our region of the galaxy
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Nebular Theory
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the idea that the solar system evolved from such a swirling cloud of dust (nebula)
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constellation
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a grouping of stars in the night sky that fall into a recognizable pattern
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planetesimal
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a small body formed from the solar nebula and eventually grew into protoplanetary bodies
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protoplanetary body
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a clump of material fromed from planetetesimals of the early stages of solar system formation that were the forerunner of today's planets
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nuclear fusion
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a nuclear proccess that releases energy when lightweight nuclei combine to form heavier nuclei during which hydrogen atoms fused to create helium atoms
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terrestrial planets
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[Mercury, Venus, Earth, and Mars] planets formed in the inner part of the solar system, consisting of mainly rocky materials
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gas giant planets
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[Jupiter, Saturn, Uranus, and Neptune] planets formed in the outer part of the solar system, composed mostly of hydrogen, helium, and methane, and having a density less than 2 gm/cm^2
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comet
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a chunk of frozen gases, ice, and rocky debris that orbits the sun found mainly in the outer solar system
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asteroid
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a small planetary body in orbit around the Sun that is larger than a meteoroid but smaller than a planet that are commonly found between the orbits of Mars and Jupiter
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Milky Way
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our gallaxy: gallaxies are classified according to their shape; elliptical, spiral, or irregular
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AGES
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Solar System - 4.5 billion years
Milky Way Galaxy - 10 billion years Universe - 12 to 14 billion years |