Quasars (pronounced kway-sars) are very brilliant, very distant astronomical objects which emit enormous amounts of energy in the form of light and radio waves. The word 'Quasar' is derived from the term QUAsi-StellAr Radio Sources. Quasars are thinly scattered in the Universe and light from most of them will have taken more than three billion years to reach Earth, so that its life may well have ended in the interim.
First discovered in 1964 their existence supports the 'Big Bang' theory of the formation of the Universe. More than 200,000 Quasars are now known, most from the Sloan Digital Sky Survey. Quasars tend to be around 10 light years in diameter, each emitting the equivalent light of 10,000 billion stars.