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 matter at densities so high that gravitational contraction is countered by the Pauli exclusion principle.
using this tag please consider whether your question would be more appropriate on the space exploration stack exchange.
Questions about gas-giant planets in very close orbit to their parent star (closer than Mercury).
Questions regarding the use of a reflective surface, for example in optics.
Questions about the Event Horizon Telescope, or EHT.
Questions regarding the phenomena by which the ratio of the orbital periods of two (or more) bodies is a fraction of small integers, because of the gravitational interactions between them.
Questions about Sagittarius A*, abbreviated Sgr A*, the "bright and very compact astronomical radio source at the center of the Milky Way" galaxy, believed to be the result of a supermassive black hol…
for questions regarding the dimming of light from distant objects when it passes through interstellar dust and gas clouds. This is not for questions about extinctions of species on Earth or other …
For questions about the observation of the sky through binoculars.
Questions regarding the non-stellar objects gravitationally bound to a star or star system.
Second lightest element in the periodic table
Questions about Europa, a moon of Jupiter with a planet-wide ocean under a thick ice crust.
a relatively inexpensive Newtonian telescope, in which the tube assembly slips freely in the lower base.
Questions regarding a theoretical 'tunnel' through spacetime which could potentially allow time travel.
Questions about the visualization tool for FITS images and data.