Three views of a quasar, animation. Quasars are the most luminous objects in the universe. They are formed by a supermassive black hole at the centre of a galaxy, which emits a huge amount of radiation in two polar jets, due to energy released by the black hole absorbing infalling matter. All quasars known are billions of light years away, meaning that they were more common earlier in the history of the universe. It is thought that they represent a stage in the formation of a galaxy, during which the central black hole rapidly absorbs material from its surroundings. Once there is not enough material left to continue to power the quasar, it becomes a normal galaxy.