What's a Quasar??
A quasi-stellar ("quasar") is a very energetic and distant active galactic nucleus. Quasars are among the most luminous objects in the universe. Quasars were first identified as being high redshift sources of eletromagnetic energy, including radio waves and visible light, that were point-like, similar to stars, rather than extended sources similar to galaxies. While there was initially some controversy over the nature of these objects—as recently as the early 1980s, there was no clear consensus as to their nature—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 discaround the black hole.
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