active galactic nucleus

(redirected from Active galaxies)
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Related to Active galaxies: Quasars

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 ?
Aimed at astronomy and physics majors, it offers thorough coverage of galactic structure and evolution, active galaxies, cosmology, and the history of the universe.
Activities include: (1) Building Perspectives with Active Galaxies; (2) Zooming In on Active Galaxies; and (3) Light Travel Time and the Size of Active Galaxies.
During the first five years - its original lifespan was only meant to be three to five years - cosmonauts and scientists pushed back the limits of knowledge on the physics of active galaxies, quasars and neutron stars, and acquired a wealth of information about living for long periods in space.
VSOP will be looking at two main groups of radio sources: active galaxies and masers.
This was the first case of what came to be called active galaxies, those with centers that seem to be the site of activity beyond the normal.
Observable properties of disc galaxies (including advances in the studies of galaxies, stellar discs of planar galaxies, gas components of disc galaxies, large-scale structures in S-galaxies, active galaxies, statistical dependences for the parameters of the galaxies):
These studies are not only driven by curiosity: Strongly magnetized electron-positron plasmas are believed to exist ubiquitously in pulsar magnetospheres and active galaxies in the Universe, and the entire Universe is believed to have been a matter-antimatter symmetric plasma in its earliest epochs after the Big Bang.
Quasars are the cores of active galaxies and are made up of supermassive black holes, (https://www.
There are plenty of active galaxies that don't follow the trends, Kormendy says, including the two spirals NGC 1068 and NGC 4151, whose black holes astronomers have studied for decades.
Special types of distant active galaxies and their innermost central regions show extreme physical processes.
Using data from NASA's Rossi X-ray Timing Explorer (RXTE) satellite, an international team has uncovered a dozen instances where X-ray signals from active galaxies dimmed as a result of a cloud of gas moving across our line of sight.
At the centers of some active galaxies, X-ray observations at wavelengths corresponding to those of fluorescent iron show that this radiation is being absorbed.