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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the group of galaxies that includes the Milky Way among others.
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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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the larger of Mars's two moons, being 11km in diameter. It is also the nearer to the planet's surface, and orbits the planet every 7 hours 39 minutes. It is predicted that within 50 million …
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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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Questions about a mathematical distribution explaining how common different masses of stars are.
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a star with an enormous mass and luminosity, showing signs of a very high rate of mass loss.