WHAT IS A QUASAR?
A quasar is an extremely bright active galactic nucleus powered by a supermassive black hole at the center of a galaxy. Gas and dust falling toward the black hole form a rapidly rotating accretion disk. Friction and intense gravitational effects heat this material to enormous temperatures, causing it to release tremendous amounts of radiation.
HOW DOES A QUASAR WORK?
Matter does not simply fall directly into the black hole. It usually forms a rotating accretion disk around it. As material moves inward, gravitational potential energy is converted into heat and radiation. This process can make the region around the black hole brighter than the combined light of all the stars in its host galaxy.
WHY ARE QUASARS SO BRIGHT?
Quasars can convert matter into radiation with remarkable efficiency compared with ordinary nuclear fusion in stars. Their intense radiation can be detected across enormous cosmic distances. Some quasars are so distant that their light has travelled for billions of years before reaching Earth.
QUASARS AS COSMIC TIME MACHINES
Because quasars can be extremely distant, astronomers observe them as they appeared when the Universe was much younger. Studying distant quasars therefore allows scientists to investigate the early growth of supermassive black holes and the evolution of galaxies.