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 about the techniques and practice of observing the night sky.
Questions regarding large spheres of plasma undergoing fusion.
Questions regarding the closest star to Earth, at the centre of the Solar System.
857 questions
Questions regarding points of extremely high mass density, which creates an extremely strong gravitational field from which light cannot escape.
778 questions
Questions regarding an object 'falling around' another object, due to a combination of gravity and momentum.
755 questions
Questions regarding Earth's only natural satellite. For questions about the natural satellites of other planets, use the tag [natural-satellite].
742 questions
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.
725 questions
Questions regarding systems of large numbers of stars held together by gravity.
Questions related to the physical instruments for astronomical observations.
Questions regarding the Sun and objects orbiting it.
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 regarding the attractive force which exists between any two bodies of matter.
590 questions
Questions about the observation of celestial objects by non-professional astronomers.
Questions regarding the planet on which humans live; the third planet from the Sun.
553 questions
Questions about the origin, history, evolution and fate of the Universe.
Questions regarding planets that lie outside the Solar System.
Questions regarding all of time and space and its contents.
The application of ballistics and celestial mechanics to the practical problems concerning the motion of rockets and other spacecraft.
334 questions
Questions regarding relatively small rocky bodies in an orbit around the Sun.
331 questions
Questions regarding electromagnetic radiation in the visible spectrum.
331 questions
Questions about observations performed in the radio frequency range of the electromagnetic spectrum.
320 questions
Questions regarding the amount of space between two objects, the units, or measurement thereof.
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…
278 questions
Questions on systems to uniquely determine position of a point or other geometric element on a manifold such as Euclidean space.
269 questions
Analysis of data is a process of inspecting, cleaning, transforming, and modeling data with the goal of discovering useful information, suggesting conclusions, and supporting decision making.
265 questions
Questions regarding the Milky Way Galaxy, the galaxy that Earth's solar system is in.
255 questions
Questions regarding stars which increase suddenly in energy output due to an explosion which ejected much of its mass.
Questions about the measurement of light waves whereby the wavelength is classified by its position in the electromagnetic spectrum.
241 questions
Questions regarding the action of or an object rotating along an axis.
237 questions
Questions regarding the history of astronomy, including discoveries and scientists.
236 questions
Questions regarding Jupiter, the 5th and largest planet in the Solar System.
235 questions
Questions regarding Mars, the fourth planet from the Sun.
230 questions
Questions about relativistic theory of gravity. General relativity describes gravity as a geometrical property of space and time.
230 questions
Questions related to the evolution of stars.
218 questions
Questions about the increase with time of distance between two distant points in the Universe.
211 questions
Questions on celestial bodies that orbit planets.
209 questions
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