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.

Type to find tags:
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A measure of the ratio of an object's mass with its volume.
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Questions regarding the amount of space between two objects, the units, or measurement thereof.
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a relatively inexpensive Newtonian telescope, in which the tube assembly slips freely in the lower base.
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× 3 × 13
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Questions regarding bodies smaller than planets but larger than other bodies, that do not meet at least one of the IAU's criteria for being a planet.
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Questions regarding the universe shortly after it's formation
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Questions regarding the planet on which humans live, the third planet from the sun.
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Questions about solar system planets/moons and exoplanets that exhibit similar features to the Earth.
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Questions about orbits with high eccentricities, which deviate greatly from perfect circles.
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Questions about the speed at which an object can go to a point at infinity while ending at rest.
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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 planets that lie outside the 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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For questions about objects or phenomena outside Earth, generally on other planets.
Questions regarding the future and ultimate fate of the Universe, including the heat death, Big Freeze, Big Rip, or Big Crunch.
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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 involving basic astronomical concepts or information.