Quasars are the most luminous objects in the universe. They are powered by supermassive black holes that can be billions of times more massive than our sun. The first quasar was discovered in 1963 by a graduate student, Maarten Schmidt, at Cal Tech.
Quasars are a type of active galactic nuclei that emits strong electromagnetic waves. They are also called quasi-stellar objects or QSOs. Quasars can be used to find black holes because they are very close to them, and as a result, they move around them in a process called gravitational lensing.