active galactic nucleus

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Related to Active galactic nuclei: quasar

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 ?
ETH researchers discovered in their extensive data collection of observed active galactic nuclei that about 5 percent appeared to be in a 'switched-off' state.
One such method proposed in the mid 1970s observed very high energy (VHE) neutrinos emitted from extraterrestrial sources such as Active Galactic Nuclei (AGN).
Current projects under his leadership include research on active galactic nuclei.
His Research interests are active galactic nuclei, galactic black-hole candidates and gamma-ray bursts.
Recent cosmological simulations have demonstrated that ""feedback"" by star formation, supernovae and active galactic nuclei appears to be critical in obtaining realistic disk galaxies, to slow down star formation to the small observed rates, to move gas and metals out of galaxies into the intergalactic medium, and to balance radiative cooling of the low-entropy gas at the centers of galaxy clusters.
In this process, the material heats up and becomes very bright -- becoming the most energetic sources of emission in the universe known as active galactic nuclei (AGN).
Those sources include active galactic nuclei, brilliantly luminous objects powered by supermassive black holes as they gather and condense huge quantities of dust and gas.
Sixty-nine papers from the October 2011 conference present research on the physical characteristics of active galactic nuclei (AGN) accretion disk winds.
In 2007 in Science, the Auger team reported a tantalizing link between incoming particles and active galactic nuclei, the violently churning, supermassive black holefueled centers of distant galaxies (SN: 11/10/07, p.
Earlier in the history of the universe, these giant, luminous black holes, called active galactic nuclei, were often much brighter and more energetic.
The combination of its superior location and experimental capabilities led to a long list of exciting discoveries of several very high energy (VHE) gamma ray sources over the past few years, including supernova remnants, the source at the Galactic Centre, compact binary systems, microquasars, pulsar wind nebulae, gamma rays from cosmic-ray interactions with dense molecular clouds, a starburst galaxy, stellar and galaxy clusters, active galactic nuclei, and "dark sources" with no obvious counterparts, in addition to conducting the first VHE survey of the sky, measuring the local cosmic-ray electron and iron nuclei spectra, constraining the level of extragalactic background light, and providing upper limits to dark mater annihilation.