Topic 7 Space

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Astronomical Unit (AU)

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A unit of distance equal to the average distance between Earth and the sun, about 150 million kilometers.

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Solar System

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The system consisting of the sun and the planets and other objects that revolve around it.

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Absolute Brightness

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The brightness a star would have if it were at a standard distance from Earth.

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Galaxy

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A huge group of single stars, star systems, star clusters, dust, and gas bound together by gravity.

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Light Year

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The distance that light travels in one year; about 9.46 trillion kilometers.

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Planetary System

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A system of planets and other celestial bodies that orbit a star.

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Stellar System

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A system of stars that are gravitationally bound to each other.

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Nebula

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A giant cloud of dust and gas in space, often the birthplace of stars.

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Luminosity

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The total amount of energy emitted by a star per unit of time.

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Relative Magnitude

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A measure of the brightness of a star as seen from Earth, compared to other stars.