A quasar is an extremely luminous active galactic nucleus, powered by a supermassive black hole, with mass ranging from millions to tens of billions of solar masses, surrounded by a gaseous accretion disc. quasar, an astronomical object of very high luminosity found in the centres of some galaxies and powered by gas spiraling at high velocity into an extremely large black hole. Quasars are among the most distant and luminous objects known. This new measurement shows that quasars can blow far past the theoretical temperature limit of 100 billion degrees Kelvin (179 billion degrees Fahrenheit), which has scientists puzzled. The term quasar originated as a contraction of "quasi-stellar [star-like] radio source" because quasars were first identified during the 1950s as sources of radio-wave emission of unknown physical origin and when identified in photographic images at visible wavelengths, they resembled faint, star-like points of light. The word quasar stands for quasi-stellar radio source. Quasars got that name because they looked starlike when astronomers first began to notice them in the late 1950s and early 60s. But quasars aren't stars. The answer is that quasars are extremely bright, up to 1,000 times brighter than our Milky Way galaxy. A Quasar are those that look like stars, but they are extremely luminous objects at all wavelengths. Pulsars are highly magnetized rotating neutron stars, while quasars are extremely powerful and distant active galactic nuclei. Quasars are bigger than pulsars. Pulsars are less bright than quasars. The Milky Way has already been a quasar. Scientists estimate that the last time Sagittarius “A” star (the supermassive Black hole at the center of our Milky Way galaxy) became a quasar was about 6 to 9 million years ago. There is a black hole behind every quasar, but not every black hole is a quasar. Such black holes are found in the centers of most large galaxies, but even then, not every galaxy hosts a quasar. Specifically, a quasar is a supermassive black hole that is actively feeding on material. They're likely to continue to exist for many many years yet. As long as the black hole has material to munch on, in fact. They do eventually disappear or at least go “dormant”, but only when material for the black hole to consume is in short supply. The current best estimate is that quasar activity is episodic, with individual episodes lasting around a million years and the total quasar lifetime lasting around 10 million years. At some point, quasar activity ceases completely, leaving behind the dormant massive black holes found in most massive galaxies. Quasars are some of the oldest, most distant, most massive and brightest objects in the universe. This quasar in particular, named P172+18, is a relic from around 780 million years after the Big Bang and reveals clues about one of the earliest ages of the universe the epoch of reionization. J0313-1806 is a cosmic treasure. In a breakthrough discovery, scientists have found the most distant quasar yet known and it's home to a seriously supermassive black hole. Astronomers led by researchers at the University of Arizona spotted the brilliant quasar about 13.03 billion light-years from Earth. The quasar's supermassive black hole, some 1.6 billion times as massive as the Sun, is the youngest on record, posing a challenge to theorists trying to explain how black holes could have grown so massive so early in cosmic history.

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