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:
× 13 × 16
× 8
A measure of the ratio of an object's mass with its volume.
× 2
× 85
Questions regarding the amount of space between two objects, the units, or measurement thereof.
× 7
a relatively inexpensive Newtonian telescope, in which the tube assembly slips freely in the lower base.
× 5
× 4 × 19 × 3 × 16
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.
× 24
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.
× 26
Questions about solar system planets/moons and exoplanets that exhibit similar features to the Earth.
× 10
Questions about orbits with high eccentricities, which deviate greatly from perfect circles.
× 3
× 4 × 5 × 8
× 4
Questions about the speed at which an object can go to a point at infinity while ending at rest.
× 2
× 5
Questions about Europa, a moon of Jupiter with a planet-wide ocean under a thick ice crust.
× 111
Questions regarding planets that lie outside the Solar System.
× 58
Questions about the increase with time of distance between two distant points in the Universe.
× 5
× 3 × 4 × 23
For questions about objects or phenomena outside Earth, generally on other planets.
× 4
Questions regarding the future and ultimate fate of the Universe, including the heat death, Big Freeze, Big Rip, or Big Crunch.
× 4
about the lack of evidence for alien life, despite the growing evidence that suitable planets are reasonably plentiful.
× 5 × 27
Questions about the dynamical processes leading to the assembling of a celestial object.