What are Quasars?

A quasar (also quasi-stellar object or QSO) is an active galactic nucleus of very high luminosity. It consists of asupermassive black hole surrounded by an orbiting accretion disk of gas. 

As gas in the accretion disk falls toward the black hole, energy is released in the form of electromagnetic radiation. 

Quasars emit energy across the electromagnetic spectrum and can be observed at radio,infrared, visible, ultraviolet, and X-ray wavelengths. 

The most powerful quasars have luminosities exceeding 1041 W, thousands of times greater than the luminosity of a large galaxy such as the Milky Way.