3C 273 is a quasar located at the center of a giant elliptical galaxy in the constellation of Virgo. It was the first quasar ever to be identified and is the visually brightest quasar in the sky as seen from Earth, with an apparent visual magnitude of 12.9. The derived distance to this object is 749 megaparsecs. The mass of its central supermassive black hole is approximately 886 million times the mass of the Sun.
Quasar 3C 273 taken by HST
3C 273 as imaged by the Hubble Space Telescope's Advanced Camera for Surveys. Light from the bright quasar nucleus is blocked by a coronagraph so that the surrounding host galaxy can be more easily seen. Credit: NASA/ESA
A quasar is an extremely luminous active galactic nucleus (AGN). It is sometimes known as a quasi-stellar object, abbreviated QSO. The emission from an AGN is powered by a supermassive black hole with a mass ranging from millions to tens of billions of solar masses, surrounded by a gaseous accretion disc. Gas in the disc falling towards the black hole heats up and releases energy in the form of electromagnetic radiation. The radiant energy of quasars is enormous; the most powerful quasars have luminosities thousands of times greater than that of a galaxy such as the Milky Way. Quasars are usually categorized as a subclass of the more general category of AGN. The redshifts of quasars are of cosmological origin.
Artist's rendering of the accretion disc in ULAS J1120+0641, a very distant quasar powered by a supermassive black hole with a mass two billion times that of the Sun
Hubble images of quasar 3C 273. At right, a coronagraph is used to block the quasar's light, making it easier to detect the surrounding host galaxy.
A cosmic mirage known as the Einstein Cross. Four apparent images are actually from the same quasar.
Quasars in interacting galaxies