What is a quasar?

A quasar is accurately defined as a distant galaxy that hosts a supermassive black hole at its center. The immense gravitational pull of this black hole attracts surrounding matter, leading to the formation of an accretion disk. As the matter spirals into the black hole, it heats up and emits vast amounts of energy, often outshining entire galaxies, thus appearing incredibly bright from Earth.

Quasars are typically found at great distances, which means they are viewed as they were in the early universe, making them critical to studies of cosmic evolution. Their brightness and distance allow astronomers to study the conditions of the early universe and understand the formation and growth of galaxies. This distinct characteristic distinguishes them from other astronomical objects, such as star clusters, irregular galaxies, or open clusters, which do not possess the same energetic phenomena associated with supermassive black holes at their centers.