Quasar Artist's rendering of ULAS J1120+0641, a very distant quasar powered by a black hole with a mass two billion times that of the Sun  . Credit: ESO /M. Kornmesser A quasi-stellar radio source ( "quasar" ) is a very energetic and distant active galactic nucleus . Quasars are extremely luminous and were first identified as being high redshift sources of electromagnetic energy , including radio waves and visible light , that were point-like, similar to stars , rather than extended sources similar to galaxies . While the nature of these objects was controversial until as recently as the early 1980s, there is now a scientific consensus that a quasar is a compact region in the center of a massive galaxy surrounding its central supermassive black hole . Its size is 10–10,000 times the Schwarzschild radius of the black hole . The quasar is powered by an accretion disc around the black hole. Quasars show a very high
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