What is a quasar?

A quasar is a bright, distant galaxy that features an active galactic nucleus, which is powered by a supermassive black hole at its center. As matter falls into this black hole, it is heated to extreme temperatures and emits enormous amounts of energy, particularly in the form of light, making quasars some of the most luminous objects in the universe. The light from quasars can take billions of years to reach Earth, allowing astronomers to study the early universe by observing them.

In contrast, other choices do not accurately describe quasars. For example, while a type of star can be incredibly bright, it does not encompass the characteristics and phenomena associated with quasars. Dark matter, while an important aspect of cosmology, does not refer to quasars. Similarly, new planets are classified differently and are not related to the characteristics of quasars. Thus, identifying a quasar as a bright, distant galaxy with a giant black hole at its center accurately captures its defining features.