Space Exploration #1

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Solar System

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The collection of eight planets and their moons in orbit around the sun, together with smaller bodies such as asteroids, meteoroids, and comets.

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Astronomical Unit (AU)

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A unit of measurement equal to 149.6 million kilometers, the mean distance from the center of the earth to the center of the sun.

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Asteroid

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A small rocky body orbiting the sun, found mainly in the asteroid belt between Mars and Jupiter.

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Comet

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A celestial object consisting of ice and dust. When near the sun, there appears to be a 'tail' of gas and dust .

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Moon

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A natural satellite that orbits a planet. Earth has one , while other planets have multiple of these.

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Sun

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The star at the center of our solar system, around which the Earth and other planets revolve.

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Planet

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A celestial body moving in an elliptical orbit around a star. In our solar system, there are eight of these recognized.

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Heliocentric

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A model of the solar system or universe having the sun as the center.

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Geocentric

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A model of the universe in which Earth is at the center of the revolving planets and stars.

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Rotation

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The spinning motion of a planet on its axis