Quasar
Quasar is a highly luminous active galactic nucleus powered by accretion onto a supermassive black hole. It is characterized by strong electromagnetic emission across a broad range of wavelengths.
Quasars are discussed in extragalactic astronomy, astrophysics, and cosmology.
Status
Quasars are observed at large cosmological distances and are used to study early galaxy formation and large-scale structure. Models of their energy production and evolution continue to be refined.