The discovery of quasars was a gradual process that took several years, from 1960 to 1963 and was eventually resolved through the discovery of their redshifts.
Away from the plane of the Milky Way Galaxy, most radio sources were identified with otherwise normal-looking galaxies. Probably the first person to note the enhanced activity in the nucleus of a galaxy was Edward Fath (1908) who reported on the nuclear emission line spectrum of NGC 1068.
Quasars are incredibly bright sources of radiation that lie at the centers of distant massive galaxies. 3C 273 is one of the strongest extragalactic sources in the sky. It was first catalogued in 1959, and the 13th magnitude optical counterpart was observed at least as early as 1887.
It was named 3C 273 because it was the 273rd entry in the third Cambridge catalog of radio sources.
Since 1960, much fainter optical counterparts were being routinely identified, using accurate radio interferometer positions which were measured primarily at the Caltech Owens Valley Radio Observatory.
In early February 1963, Maarten Schmidt at Caltech recognized that the spectrum of the 13th magnitude apparently stellar object identified with the radio source 3C 273 could be most easily interpreted by a redshift of 0.16. He used the Hale optical telescope at California's Mount Palomar observatory to puzzle it all out.
3C 273 eluded identification until the series of lunar occultation observations led by Cyril Hazard.
An accurate position had been obtained in August, 1962 by Hazard, Mackey, and Shimmins (1963), who used the 210-foot antenna at the Parkes station in Australia to observe a lunar occultation of 3C 273.
Subsequent work by Schmidt and others led to increasingly-large measured redshifts and the recognition of the broad class of active galactic nuclei (AGN) of which quasars occupy the high luminosity end.
Discovery of quasars
