QUASARS
Incredibly powerful, massive black holes may, astronomers think, be found lurking at the centres of galaxies. There could even be one at the centre of our own Milky Way Galaxy. Astronomers have detected a ring of fast-moving, hot gas swirling around the centre. The ring of gas is probably in the grip of a powerful gravitational pull – most likely, astronomer’s suspect, to be the work of a black hole.
The activity at the centre of our Galaxy is as nothing compared to that of quasars. These objects look like stars, but they lie at incredible distances from us: the farthest quasars are 13 billion light years away. To be visible at that distance means they must be giving off immense amounts of energy. Quasars are the centres of extremely violent galaxies containing super-massive black holes, weighing up to 100 billion Suns. The brilliant light comes from the disc of hot gas and dust spiralling into the black hole.
Black holes are invisible, but it is possible to detect them by studying their effects, astronomers observing a star called Cygnus X-1 saw that it was giving off enormous amounts of energy (a sure sign of violent activity in the Universe). They discovered that this huge, hot blue star was being dragged around in a circle by an unseen object with a huge gravitational pull. That unseen object, astronomers now believe, is a black hole, which is tearing gas from the star. The gas forms a whirling disc before plummeting into the black hole. As it falls, it travels faster and faster until it moves almost at the speed of light itself. Close to the hole, the gas becomes so hot it emits massive amounts of energy.
Picture Credit : Google