active galactic nucleus


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active galactic nucleus

(AGN) See active galaxy.

active galactic nucleus

[¦ak·tiv gə‚lak·tik ′nü·klē·əs]
(astronomy)
A central region of a galaxy, a light-year or less in diameter, where violent and apparently explosive behavior is observed which is manifested in many ways, including the high-velocity outflow of gas, strong nonthermal radio emission, intense and often polarized and highly variable radiation over a wide range of wavelength bands, and ejection of jets of relativistic material.
References in periodicals archive ?
2006) The effect of stellar feedback and quasar winds on the active galactic nucleus population.
It seemed to be a starless blob of fluorescing intergalactic gas, most likely lit by a quasar-like active galactic nucleus in IC 2497 (see image at right).
The spectrum attests to X-rays being scattered or reprocessed by the giant molecular cloud, and it suggests that Sgr A* once was as luminous as a typical active galactic nucleus.
NGC 4438 may also have an active galactic nucleus, wreaking further havoc.
M87 has the only very active galactic nucleus within this distance.
Veteran variable-star observers long have known that the nominally 13th-magnitude galaxy Markarian 421 contains the brightest and most variable active galactic nucleus (AGN) visible in backyard telescopes (S&T: May 1993, page 75).
If some cosmic event were to dump a new load of gaseous fuel into our galaxy's core, the central black hole would almost certainly flare back up, shining brightly as an active galactic nucleus for millions of years.
16~ centimeter wavelength) have been discovered coming from a few objects including pulsars and the active galactic nucleus Markarian 421 (May issue, page 75).
Based on theoretical studies and observations in the radio, X-ray, and gamma-ray spectral regions, astronomers had come to think of Sgr A* as a miniature version of an active galactic nucleus -- a massive black hole encircle by a hot accretion disk.