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:
× 224
Questions regarding large spheres of gas undergoing fusion.
× 166
Questions regarding an object 'falling around' another object, due to a combination of gravity and momentum.
× 160
Questions regarding Luna, Earth's moon and only natural satellite.
× 148
Questions regarding the earthly Sun and objects orbiting it.
× 141
Questions regarding the closest star to Earth, at the centre of the Solar System.
× 135
Questions regarding the attractive force which exists between any two bodies of matter.
× 132
Questions regarding systems of large numbers of stars held together by gravity.
× 120
Questions regarding celestial bodies in orbit around a star.
× 117
Questions regarding the planet on which humans live, the third planet from the sun.
× 116
Questions regarding points of extremely high mass density, which creates an extremely strong gravitational field from which light cannot escape.
× 107
Questions related to the physical instruments for astronomical observations.
× 104
Questions regarding the space in which all mass is thought to exist.
× 90
Questions regarding the action or process of observing a single object carefully to glean information.
× 86
Questions regarding planets that lie outside the Solar System.
× 80
Questions about the origin, history, evolution and fate of the Universe.
× 80
Questions regarding electromagnetic radiation in the visible spectrum.
× 70
Questions about the observation of celestrial objects by non-professional astronomers.
× 66
Questions regarding the amount of space between two objects, the units, or measurement thereof.
× 54
Questions regarding the Milky Way Galaxy, the galaxy that Earth's solar system is in.
× 51
Questions regarding the currently prevalent cosmological model for the origin of the universe.
× 50
Questions involving the physics of the universe, especially the nature of astronomical objects, energy fields, and/or regions, rather than their positions or motions in space.
× 50
Questions involving basic astronomical concepts or information.
× 50
Questions about relativistic theory of gravity. General relativity describes gravity as a geometrical property of space and time.
× 48
The near-vacuum extending between the planets and stars, containing small amounts of gas and dust. Also called outer space to refer to the physical universe beyond the Earth's atmosphere.
× 46
Icy bodies that usually consist of methane, water, and other materials that originate from beyond the jovian planets, and occasionally fall into the inner solar system giving off a massive tail as mat…
× 45
Questions regarding a layer of gasses surrounding a celestial object.
× 45
Questions regarding the 4-dimensional background structure of our universe.
× 44
Questions regarding relatively small rocky bodies in an orbit around the Sun.
× 44
Questions regarding Jupiter, the 5th and largest planet in Earth's solar system.
× 41
Questions about the increase with time of distance between two distant points in the Universe.
× 39
Questions regarding Mars, the fourth planet from the sun.
× 38
Questions regarding stars which increase suddenly in energy output due to an explosion which ejected much of its mass.
× 37
Questions regarding the action of or an object rotating along an axis.
× 35
Questions about observation performed in the radio frequency range of the electromagnetic spectrum (between 10 MHz and 1GHz).
× 33
Questions about the source or effects of the matter that makes up 85% of the matter in the universe but appears to only interact gravitationally.
× 30
Questions regarding the phenomenon in the early universe characterized by an extreme expansion of space.