active galactic nucleus(redirected from Active galactic nuclei)
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Related to Active galactic nuclei: quasar
active galactic nucleus(AGN) See active galaxy.
Collins Dictionary of Astronomy © Market House Books Ltd, 2006
active galactic nucleus[¦ak·tiv gə‚lak·tik ′nü·klē·əs]
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.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.