A tag is a keyword or label that categorizes your question with other, similar questions. Using the right tags makes it easier for others to find and answer your question.

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Questions regarding undesired brightening of the night sky inhibiting observation of astronomical objects.
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the group of galaxies that includes the Milky Way among others.
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Questions about gas-giant planets in very close orbit to their parent star (closer than Mercury).
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Late Heavy Bombardment; occurring between 3.7-4 billion years ago when the inner solar system underwent heavy asteroidal impacts. Also know as the Lunar Cataclysm.
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Questions about Europa, a moon of Jupiter with a planet-wide ocean under a thick ice crust.
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A measure of the ratio of an object's mass with its volume.
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track and display the current time.
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Questions regarding Charon, the largest satellite of the dwarf planet Pluto. Often considered to be Pluto's binary.
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Questions regarding the Sombrero Galaxy, also known as M104 or NGC 4594. It is an unbarred spiral galaxy, part of the Virgo constellation.
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