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:
× 328
Questions regarding large spheres of plasma undergoing fusion.
× 236
Questions on astronomical objects orbiting a star massive enough to be rounded, not massive enough to cause fusion, and which have cleared its orbit of planetesimals.
× 228
Questions regarding an object 'falling around' another object, due to a combination of gravity and momentum.
× 223
Questions regarding the Sun and objects orbiting it.
× 219
Questions regarding the closest star to Earth, at the centre of the Solar System.
× 213
Questions regarding Luna, Earth's moon and only natural satellite.
× 208
Questions regarding the attractive force which exists between any two bodies of matter.
× 198
Questions regarding points of extremely high mass density, which creates an extremely strong gravitational field from which light cannot escape.
× 174
Questions regarding the planet on which humans live, the third planet from the sun.
× 162
Questions regarding systems of large numbers of stars held together by gravity.
× 154
Questions regarding the space in which all matter is thought to exist.
× 152
Questions related to the physical instruments for astronomical observations.
× 126
Questions regarding the action or process of observing a single object carefully to glean information.
× 115
Questions about the observation of celestrial objects by non-professional astronomers.
× 114
Questions regarding planets that lie outside the Solar System.
× 110
Questions regarding electromagnetic radiation in the visible spectrum.
× 108
Questions about the origin, history, evolution and fate of the Universe.
× 91
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.
× 87
Questions regarding the amount of space between two objects, the units, or measurement thereof.
× 80
Questions regarding the 4-dimensional background structure of our universe.
× 78
Questions about relativistic theory of gravity. General relativity describes gravity as a geometrical property of space and time.
× 76
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.
× 73
Questions involving basic astronomical concepts or information.
× 72
Questions regarding relatively small rocky bodies in an orbit around the Sun.
× 72
Questions regarding the Milky Way Galaxy, the galaxy that Earth's solar system is in.
× 71
Questions regarding the currently prevalent cosmological model for the origin of the universe.
× 63
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…
× 62
Questions regarding Jupiter, the 5th and largest planet in Earth's solar system.
× 60
Questions regarding a layer of gasses surrounding a celestial object.
× 59
Questions about the increase with time of distance between two distant points in the Universe.
× 58
Questions regarding the action of or an object rotating along an axis.
× 57
Questions regarding Mars, the fourth planet from the sun.
× 54
Questions regarding stars which increase suddenly in energy output due to an explosion which ejected much of its mass.
× 50
Questions related to the evolution of stars.
× 49
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.
× 48
Questions regarding the property of astronomical objects that determines their inertial resistance and gravitational interaction with other bodies.