Quasar

A quasar (contraction of QUASi-stellAR radio source) is an extremely bright and distant active nucleus of a young galaxy. They were first identified as being high-redshift sources of electromagnetic energy, including radio waves and visible light that were point-like similar to stars rather than extended sources similar to galaxies. While there was initially some controversy over the nature of these objects, there is now a scientific consensus that a quasar is a compact halo of matter surrounding the central supermassive black hole of a young galaxy.