quasar

A quasar is a very luminous and distant celestial body whose flux can vary spectacularly. It is an active nucleus of a galaxy, i.e. a supermassive black hole, exerting a considerable force of attraction on all the surrounding objects and which accretes matter. This accretion forms a disc of particles rotating at very high speeds before being swallowed up. Quasars emit radiation that can be seen several billions of light years away.