Answer to Question #89485 in Astronomy | Astrophysics for ashish

Question

Define an active galaxy. What is the source of its activity?

Answer 1

Active galaxies have a small core of emission embedded at the center of an otherwise typical galaxy. This core is called an "active galactic nucleus". The core very bright compared to the rest of the galaxy. The radiation from an active galactic nucleus is believed to result from the accretion of matter by a supermassive black hole at the center of its host galaxy.