Any of a class of enigmatic cosmic objects of high luminosity and strong radio emission observed at extremely great distances; also, a closely related object that has the same optical appearance but does not emit radio waves, i.e., a so-called quasi-stellar object (QSO). Most quasars exhibit very large redshifts, suggesting that they are moving away from Earth at tremendous speeds (approaching the speed of light); they thus are some of the most distant known objects in the universe. Quasars are no more than a light-year or two across but as much as 1,000 times more luminous than a giant galaxy having a diameter of 100,000 light-years; their extreme brightness allows them to be observed at distances of more than 10 billion light-years. Many investigators attribute such energy generation to matter spiraling at high velocity into a supermassive black hole (millions or billions of times as much mass as the Sun) at the centre of a distant galaxy. See also active galactic nucleus.
Variants of QUASAR
quasar in full quasi-stellar radio source
This entry comes from Encyclopædia Britannica Concise.
For the full entry on quasar, visit Britannica.com.
Seen & Heard
What made you look up quasar? Please tell us what you were reading, watching or discussing that led you here.