What is a quasar?
Q: What is a quasar?
A: A quasar, or quasi-stellar radio source, is an active galactic nucleus (AGN) that is the most energetic and distant type of AGN. They are quite small in comparison with the energy they put out, and are not much larger than the Solar System.
Q: How far away can quasars be found?
A: The highest redshift quasar known as of June 2011 was about 29 billion light-years from Earth.
Q: What is the mechanism behind their brightness changes?
A: The mechanism of brightness changes probably involves relativistic beaming of jets pointed nearly directly toward us.
Q: What is believed to be at the center of a quasar?
A: Scientists now agree that a quasar is a compact region in the center of a massive galaxy surrounding a central supermassive black hole. Its size is 10–10,000 times the Schwarzschild radius of this black hole.
Q: Where does its energy come from?
A: The energy emitted by a quasar comes from gravitational energy created from mass falling onto an accretion disc around the black hole.
Q: How luminous are they compared to other galaxies?
A: Quasars are extremely luminous and can be 100 times greater than that of our Milky Way galaxy.
Q: Why were they more common in early universe?
A: Quasars were more common in early universe because this energy production ends when the supermassive black hole consumes all of the gas and dust near it, meaning most galaxies may have gone through an active stage as one or some other class of active galaxy before becoming dormant due to lack of matter to feed into their central black holes for radiation production.
