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active galaxy
(redirected from Active galactic nucleus)

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active galaxy

In astronomy, type of galaxy that emits vast quantities of energy from a small region at its centre, the active galactic nucleus (AGN). Active galaxies are subdivided into radio galaxies, Seyfert galaxies, BL Lacertae objects, and quasars.

Active galaxies are thought to contain black holes with a mass 108 times that of the Sun, drawing stars and interstellar gas towards them in a process of accretion. The gravitational energy released by the in-falling material is the power source for the AGN. Some of the energy may appear as a pair of opposed jets emerging from the nucleus. The orientation of the jets to the line of sight and their interaction with surrounding material determines the type of active galaxy that is seen by observers. See also starburst galaxy.



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? Mentioned in ? References in periodicals archive
 
Jaffe of the State University of Leiden in the Netherlands, the Hubble image provides the closest look yet at the center of a type of galaxy -- called an active galactic nucleus (AGN) -- that has a luminous, energetic core.
Orbiting Hubble eyes active galaxy's disk by Cowen, Ron / Science News
According to Begelman's theoretical analysis, each of these disk configurations can develop out of different initial conditions, and it may be the disk configuration that determines what kind of active galactic nucleus we see in a given instance.
Getting to the bottom of supermassive black holes by Thomsen, Dietrich E. / Science News
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