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.
Questions regarding large spheres of plasma undergoing fusion.
Questions about the techniques and practice of observing the night sky.
Questions regarding the closest star to Earth, at the centre of the Solar System.
Questions regarding an object 'falling around' another object, due to a combination of gravity and momentum.
Questions regarding points of extremely high mass density, which creates an extremely strong gravitational field from which light cannot escape.
Questions regarding Earth's only natural satellite. For questions about the natural satellites of other planets, use the tag [natural-satellite].
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.
Questions regarding systems of large numbers of stars held together by gravity.
Questions regarding the Sun and objects orbiting it.
Questions related to the physical instruments for astronomical observations.
Questions regarding the attractive force which exists between any two bodies of matter.
Questions regarding the planet on which humans live; the third planet from the Sun.
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.
Questions about the observation of celestial objects by non-professional astronomers.
Questions regarding planets that lie outside the Solar System.
Questions about the origin, history, evolution and fate of the Universe.
Questions regarding all of time and space and its contents.
Questions regarding electromagnetic radiation in the visible spectrum.
Questions regarding relatively small rocky bodies in an orbit around the Sun.
Questions regarding the amount of space between two objects, the units, or measurement thereof.
Questions about observations performed in the radio frequency range of the electromagnetic spectrum.
The application of ballistics and celestial mechanics to the practical problems concerning the motion of rockets and other spacecraft.
Questions about photography of celestial objects by amateur or professional astronomers. Questions about photography of other objects are off-topic but might be asked on our sister site Photography St…
Questions regarding the Milky Way Galaxy, the galaxy that Earth's solar system is in.
Questions on systems to uniquely determine position of a point or other geometric element on a manifold such as Euclidean space.
Questions regarding stars which increase suddenly in energy output due to an explosion which ejected much of its mass.
Questions regarding Mars, the fourth planet from the Sun.
Questions regarding the history of astronomy, including discoveries and scientists.
Questions regarding Jupiter, the 5th and largest planet in the Solar System.
Questions regarding the 4-dimensional background structure of our universe.
Questions regarding the action of or an object rotating along an axis.
Questions on celestial bodies that orbit planets.
Questions about relativistic theory of gravity. General relativity describes gravity as a geometrical property of space and time.
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…
Questions about the measurement of light waves whereby the wavelength is classified by its position in the electromagnetic spectrum.
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.