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Definition: A quasar is an astronomical entity that emits incredibly high levels of electromagnetic radiation (including light). The amount of energy emitted by a quasar dwarfs even the brightest stars, making them favorites of astrophysicists and cosmologists who wish to study distant space.

There are over 60,000 known quasars, all of which appear to be very distant from us (based upon the observed redshift). The closest known quasar is 780 million light-years away.

Many scientists believe that a quasar is created by matter interacting with supermassive black holes. This would appear to explain the high energy output and the rapid variability observed in their luminosity. The quasar is formed when matter falling into the black hole is flung back out, creating superheated beams of energy.

A quasar that points directly toward the Earth is called a blazar.

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