A Quasi-stellar object abbreviated as QSO. It is an extremely luminous AGN (Active Galactic Nuclei), in which a supermassive black hole is situated with a mass ranging from millions to billions of solar masses. The supermassive black hole at the centre is smothered by a gaseous accretion disk, where the objects are accelerated nearly to the speed of light. Quasars were first identified during the 1950s as sources of radio wave emissions. They have a star-like structure when viewed through a telescope. The quasars may represent a stage in the evolution of some galaxies.