Quasar, KWAY sahr or KWAY zahr, is an extremely luminous object at the center of some distant galaxies. The word quasar is a shortened form of the term quasi-stellar (starlike) radio source, which was applied to the first type of quasar identified. Because quasars look much like stars in photographs, they are sometimes called quasi-stellar objects. Most quasars are about the size of the solar system. But they can be a trillion times brighter than the sun. Many astronomers believe quasars are the most distant objects yet detected in the universe. Some are estimated to be as far as 12 billion to 16 billion light-years from the earth