Quasar

Quasar, or quasi-stellar object, a starlike celestial object whose spectrum seen telescopically shows an abnormally large red shift. Quasars may be extremely distant objects—perhaps the inexplicably bright cores of galaxies near the limits of the known universe—receding from Earth at high velocities (which would account for the red shift). Quasars also show variability in light and radio emission. (Although the first quasars were discovered by radio astronomy, not all are radio sources. These phenomena might indicate that quasars are comparatively small objects comparatively close to us (large and more distant objects being unlikely to vary in this way). There are about 200 quasars in each square degree of the sky.

See also: Astronomy; Red shift.