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 about gas-giant planets in very close orbit to their parent star (closer than Mercury).
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the group of galaxies that includes the Milky Way among others.
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about the lack of evidence for alien life, despite the growing evidence that suitable planets are reasonably plentiful.
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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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Questions regarding the National Aeronautics and Space Administration, the American civilian space agency.
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Questions regarding a theoretical 'tunnel' through spacetime which could potentially allow time travel.
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Space debris (also known as "orbital debris", "space junk", or "space waste") is the collection of defunct objects in orbit around Earth and includes everything from spent rocket stages, old satellite…
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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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