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15 Cards in this Set
- Front
- Back
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accretion
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the gradual accumulation of matter by an astronomical body, usually caused by gravity
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asteroid
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any of the rocky objects larger than a few hundred meters in diameter that orbits the sun
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asteroid belt
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the 1 1/2 astronomical-unit-wide region between the orbits of Mars and Jupiter in which most of the asteroids are found
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average density
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the mass of an object divided by its volume
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comet
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a small body of ice and dust in orbit about the sun
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crater
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a circular depression on a celestial body caused by the impact of a meteoroid, asteroid, comet, or volcano
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meteoroid
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a small rock in interplanetary space
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orbital inclination
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the tilt or angle of an object's orbital plane around the sun compared to the ecliptic
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planetesimal
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primordial asteroidlike object from which the planets accreted
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protoplanet
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the embryonic stage of a planet when it is growing because of collisions with planetesimals
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protoplanetary disks
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a disk of material encircling a protostar or a newborn star.
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protosun
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the sun prior to the time when hydrogen fusion began in its core
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solar nebula
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the cloud of gas and dust from which the sun and the rest of the solar system formed
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solar system
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the sun, planets, their satellites, asteroids, comets, and related objects that orbit the sun
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terrestrial planet
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any of the planets Mercury, Venus, Earth, or Mars; a planet with a composition and density similar to Earth
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