AGN (other)
AGN may refer to: * Active galactic nucleus * Acute glomerulonephritis * Agutaynen language * Allergan (stock symbol AGN) * Angoon Seaplane Base Angoon Seaplane Base is a state-owned public-use seaplane base located one nautical mile (2 kilometre, km) southeast of the central business district of Angoon, Alaska, Angoon, a city on Admiralty Island in the Hoonah-Angoon Census Are ...

Active Galactic Nucleus
An active galactic nucleus (AGN) is a compact region at the center of a galaxy that has a much-higher-than-normal luminosity over at least some portion of the electromagnetic spectrum with characteristics indicating that the luminosity is not produced by stars. Such excess non-stellar emission has been observed in the radio, microwave, infrared, optical, ultra-violet, X-ray and gamma ray wavebands. A galaxy hosting an AGN is called an "active galaxy". The non-stellar radiation from an AGN is theorized to result from the accretion of matter by a supermassive black hole at the center of its host galaxy. Active galactic nuclei are the most luminous persistent sources of electromagnetic radiation in the universe, and as such can be used as a means of discovering distant objects; their evolution as a function of cosmic time also puts constraints on models of the cosmos. The observed characteristics of an AGN depend on several properties such as the mass of the central black hole, ...
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