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 Europa, a moon of Jupiter with a planet-wide ocean under a thick ice crust.
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Planets that lie outside our solar system.
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Questions about the increase with time of distance between two distant points in the Universe.
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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 the dynamical processes leading to the assembling of a celestial object.
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Questions regarding systems of large numbers of stars held together by gravity.
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Questions regarding gravitationally bound systems of hundreds to thousands of galaxies as well as interactions between such systems.
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Questions about relativistic theory of gravity. General relativity describes gravity as a geometrical property of space and time.
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Questions regarding the attractive force which exists between any two bodies of matter.
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Questions about the "Goldilocks Zone" around a parent star where conditions are just right for the potential of life developing.
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Questions regarding thermal energy and its effect on astronomical objects.
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Questions about gas-giant planets in very close orbit to their parent star (closer than Mercury).
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Questions regarding the Hubble space telescope, a scientific telescope on a satellite orbiting Earth.