3C48 is a

quasar A quasar is an extremely Luminosity, luminous active galactic nucleus (AGN). It is pronounced , and sometimes known as a quasi-stellar object, abbreviated QSO. This emission from a galaxy nucleus is powered by a supermassive black hole with a m ...

discovered in 1960; it was the second source conclusively identified as such. 3C48 was the first source in the

Third Cambridge Catalogue of Radio Sources The Third Cambridge Catalogue of Radio Sources (3C) is an astronomical catalogue of celestial radio sources detected originally at 159 MHz, and subsequently at 178 MHz. History 3C The catalogue was published in 1959 by members of the ...

for which an optical identification was found by

Allan Sandage Allan Rex Sandage (June 18, 1926 – November 13, 2010) was an American astronomer. He was Staff Member Emeritus with the Carnegie Observatories in Pasadena, California. He determined the first reasonably accurate values for the Hubble consta ...

and

Thomas A. Matthews Thomas A. Matthews is an American astronomer. He is credited with being one of the discoverers of the first quasar, 3C 48, in 1960 using a new interferometer at the Owens Valley Radio Observatory, along with Allan Sandage. Matthews received his ...

in 1960 through

interferometry Interferometry is a technique which uses the ''interference'' of superimposed waves to extract information. Interferometry typically uses electromagnetic waves and is an important investigative technique in the fields of astronomy, fiber opt ...

Jesse L. Greenstein Jesse Leonard Greenstein (October 15, 1909 – October 21, 2002) was an American astronomer. His parents were Maurice G. and Leah Feingold. He earned a Ph.D, with thesis advisor Donald H. Menzel, from Harvard University in 1937, having start ...

and Thomas Matthews found that it had a redshift of 0.367, making it one of the highest redshift sources then known. It was not until 1982 that the surrounding faint galactic "nebulosity" was confirmed to have the same redshift as 3C48, cementing its identification as an object in a distant galaxy. This was also the first solid identification of a quasar with a surrounding galaxy at the same redshift. 3C 48 is one of four primary calibrators used by the

Very Large Array The Karl G. Jansky Very Large Array (VLA) is a centimeter-wavelength radio astronomy observatory located in central New Mexico on the Plains of San Agustin, between the towns of Magdalena and Datil, ~ west of Socorro. The VLA comprises twen ...

(along with 3C 138 and 3C 147, and 3C 286). Visibilities of all other sources are calibrated using observed visibilities of one of these four calibrators.

References

{{reflist Quasars 048 Astronomical objects discovered in 1960 Triangulum (constellation)