Gas in the disc falling towards the black hole heats up and releases energy in the form of electromagnetic radiation.
The emission from an AGN is powered by a supermassive black hole with a mass ranging from millions to tens of billions of solar masses, surrounded by a gaseous accretion disc. It is sometimes known as a quasi-stellar object, abbreviated QSO. A quasar ( / ˈ k w eɪ z ɑːr/ KWAY-zar) is an extremely luminous active galactic nucleus (AGN).
