Description: Short for quasi-stellar radio source, quasars are distant extragalactic sources. Quasars appear as stars (hence, quasi-stellar) and were initially detected with radio telescopes. Observations reveal that they are associated with the region around the most massive supermassive black holes at the center of galaxies. Quasars are a subclass of active galactic nuclei (AGN), which includes radio and Seyfert galaxies, blazars, and low-ionization nuclear emission-line regions (LINERs). Quasars can be as much as 100 times more luminous than their host galaxy. Some also have giant jets which interact with the gas around and within their host galaxy. Because of their high luminosities, quasars can be used to study distant galaxies, intervening galaxies, and the intergalactic medium. 3C 273 was the first quasar detected.

Related Terms:

• Active Galactic Nucleus
• Black Hole
• Radio Astronomy

Term and definition status: This term and its definition have been approved by a research astronomer and a teacher

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