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12 Cards in this Set
- Front
- Back
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Galaxy
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A collection of stars, dust, and gas bound together by gravity.
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Astronomical unit
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The average distance between the Earth and the sun; approximately 150 million kilometers (symbol, AU).
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Electromagnetic spectrum
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All of the frequencies or wavelengths of electromagnetic radiation.
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Telescope
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An instrument that collects electromagnetic radiation and concentrates it for better observation.
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Refracting telescope
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A telescope that uses a set of lenses to gather and focus light from distant objects.
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Reflecting telescope
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A telescope that uses a curved mirror to gather and focus light from distant objects.
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Rotation
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The spin of a body on its axis.
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Revolution
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The motion of a body that travels around another body in space; one complete trip along an orbit.
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Perihelion
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The point in the orbit of a planet at which the planet is closest to its sun.
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Aphelion
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The point in the orbit of a planet at which the planet is farthest from its sun.
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Equinox
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The moment when the sun appears to cross the celestial equator (a line directly overhead the equator an Earth). The hours of daylight and darkness are approximately equal everywhere on Earth on that day.
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Solstice
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The point at which the sun is as far North or as far South of the equator as possible.
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