An American Astronomer, Allan R Sandage in 1960 observed very strong Radio Emissions to be coming from certain localized direction in the sky. He used a Photographic Plate to view these emissions, which appeared similar to Stars. But they were not actually stars, as proved by their other characteristics including a large Red Shift.
He then found out the actual position of these Star-like objects using Optical Photographs. This led to the discovery of a new class of objects in the Universe, termed as Quasars meaning Quasi-Stellar Sources. These Quasars had their Angular Diameter less than that of 1 Second of an Arc, which is more or less similar to that of Stars. Due to this, they, like Stars appeared on the Photograph unresolved point-like objects.
Later in 1962, Maarten Schimdt identified a much brighter star-like object termed as 3C273, with the help of a Radio Telescope in Australia. Its Red Shift was measured to be 0.158, which was far larger than any other that had been detected for ordinary Galaxies. These two observations confirmed the existence of Quasars.
Characteristics
Quasars are generally much Bluer than most of the Stars except the White Dwarf Stars. They consist of a massive Nucleus with a total size of less than a light-year. Quasars are surrounded by an extended halo of gas excited by the energy radiated by the central object. Some Quasars emit significant amount of energy at Radio Frequencies ranging from about 30 MHZ to 100 GHZ. The energy emitted by Quasars is believed to be Gravitational instead of Thermonuclear in origin.
