View source for 3C 48

{{Quasar
  | name = [[Third Cambridge Catalogue of Radio Sources|3C]] 48
  | image = Radio map of quasar 3C48.jpg
  | epoch = [[J2000]]
  | ra = {{RA|01|37|41.1}}<ref name="ned">{{cite web
  | title=NASA/IPAC Extragalactic Database
  | work=Results for 3C 48
  | url=http://nedwww.ipac.caltech.edu/cgi-bin/nph-objsearch?objname=3C+48&extend=no
  | access-date=2006-10-26 }}</ref>
  | dec = {{DEC|+33|09|32}}<ref name="ned" />
  | constellation name = [[Triangulum]]
  | z = 110,024 ± 0 km/[[second|s]]<ref name="ned" /><br/>0.367<ref name="ned" />
  | type = E<ref name=SIMBAD>{{cite simbad|title=3C 48}}</ref>
  | dist_ly = 3.9 [[Giga-|billion]] [[light-year]]s<br/>([[Light travel time]])<ref name=ned/><br/>4.5 billion light-years<br/>([[Comoving distance|present]])<ref name=ned/>
  | appmag_v = 16.2
  | size_v = 0.6´X0.5´
  | notes = First quasar discovered
  | names = [[PG (star catalog)|PG]] 0134+329, [[Quasar|QSO]] B0134+329, [[Principal Galaxies Catalogue|PGC]] 73991
}}

'''3C48''' is a [[quasar]] discovered in 1960; it was the second source conclusively identified as such.<ref>{{cite journal | last = Weaver | first = Kenneth F. |author-link=Kenneth Weaver|date=May 1974 | title = The Incredible Universe | journal=[[National Geographic (magazine)|National Geographic]] | number =   5 | volume = 145 | pages = 589–633}}</ref>

3C48 was the first source in the [[Third Cambridge Catalogue of Radio Sources]] for which an optical identification was found by [[Allan Sandage]] and [[Thomas A. Matthews]] in 1960 through [[interferometry]].<ref>{{cite journal
 | author= Matthews, Thomas A.
 | author-link= Thomas A. Matthews
 | author2= Sandage, Allan R.
 | author2-link= Allan Sandage
 | title=Optical Identification of 3c 48, 3c 196, and 3c 286 with Stellar Objects
 | date=1963
 | journal=[[The Astrophysical Journal]]
 | volume=138
 | pages=30–56
 | doi=10.1086/147615
 | bibcode=1963ApJ...138...30M
 | doi-access=free
 }}</ref>
In 1963 [[Jesse L. Greenstein]] and Thomas Matthews found that it had a redshift of 0.367, making it one of the highest redshift sources then known.<ref>{{cite journal
 | author=Greenstein, J. L.
 | author-link=Jesse L. Greenstein
 |author2=Matthews, Thomas A.
 |author2-link=Thomas A. Matthews
 | title=Red-Shift of the Unusual Radio Source 3C48
 | date=1963
 | journal=[[Nature (journal)|Nature]]
 | volume=197
 | issue=4872
 | pages=1041–1042
 | bibcode=1963Natur.197.1041G
 | doi=10.1038/1971041a0
 | s2cid=4193798
 }}</ref>
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.<ref>{{cite journal
 | author=Todd A. Boroson
 | author2=Oke, J. B.
 | name-list-style=amp
 | title=Detection of the underlying galaxy in the QSO 3C48
 | journal=[[Nature (journal)|Nature]]
 | volume=296
 | issue=5856
 | pages=397–399
 | bibcode=1982Natur.296..397B
 | doi=10.1038/296397a0
 | date=1982| s2cid=4284238
 }}</ref>  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]] (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.<ref name="NRAO">{{cite web |last=Witz |first=Stephan W. |title=Calibration and Flux Density Scale |publisher=[[National Radio Astronomy Observatory]] |date=4 December 2015 |url=https://science.nrao.edu/facilities/vla/docs/manuals/oss/performance/fdscale |access-date=15 May 2016}}</ref>

== Nomenclature ==
The name of the object “3C 48” consists of two significant parts. The first part, “3C,” means that the object belongs to the [[Third Cambridge Catalogue of Radio Sources|Third Cambridge Catalog of Radio Sources]]. The second part - “48” - is the serial number in the catalog ordered by [[right ascension]].

== History ==
 '''3C 48''' was the first source in the [[Third Cambridge Catalogue of Radio Sources|Third Cambridge Catalog of Radio Sources]] to be optically identified by Allan Sandage and Thomas Matthews in 1960 using interferometry. 

[[Jesse L. Greenstein|Jesse Greenstein]] and Thomas Matthews found that it had a redshift of 0.367, one of the highest redshifts of any source known at the time. It was not until 1982 that a surrounding faint galactic "nebula" was measured to have the same redshift as 3C 48, confirming its identification as an object in a distant galaxy. This was also the first reliable identification of a quasar with a surrounding galaxy of the same redshift.<ref>{{Cite web |year=1963 |title=Optical Identification of 3c 48, 3c 196, and 3c 286 with Stellar Objects |url=http://adsabs.harvard.edu/abs/1963ApJ...138...30M |archive-url=https://web.archive.org/web/20190712185628/http://adsabs.harvard.edu/abs/1963ApJ...138...30M |archive-date=2019-07-12 |series=[[The Astrophysical Journal]] |publisher=[[IOP Publishing]] |pages=30-56 |language=English |type=journal |doi=10.1086/147615}}</ref>

{{Quote|text=On September 26, 1960, Matthews and Sandage photographed an area of the sky containing one such source, 3C48, with the 200-inch telescope. To their surprise, there were no objects within the error rectangle of the coordinates in this area except for a star of 16.2<sup>m</sup>. True, there were traces of a faint small nebula around it, but the object certainly looked like a star. Doubts about the possibility of identifying the radio source with a star disappeared on October 22, 1960, when Sandage obtained the [[spectrum]] of the object. It contained an unusual combination of broad [[Emission spectrum|emission lines]] that defied identification. The [[Color Index|The color indices]] of 3C48 were also unusual: Sandage found that they were consistent with hot [[White Dwarf|white dwarfs]] and former [[Nova]] - very hot objects with an [[Ultraviolet Radiation|ultraviolet]] excess.

In December 1960, Sandage reported the results of the first optical observations of 3C48 at the 107th meeting of the [[American Astronomical Society]]. Testing the hypothesis that 3C48 is a stellar remnant of a nova or even a [[supernova]] ("the first true [[radio star]]"), H. Smith and D. Hoffleit looked through the Harvard Sky Survey's collection of plates for 1897-1958 and did not find any noticeable fluctuations in the object's brightness exceeding 0.3m, which are common in former novae. The most likely possibility seemed to be that it was a neutron star - a remnant of a [[supernova]].|author=[[Yu. N. Efremov]]|title=Into the Universe|source=https://archive.org/details/isbn_535400392X_844}}

== References ==

{{reflist}}

[[Category:Quasars]]
[[Category:3C objects|048]]
[[Category:Astronomical objects discovered in 1960]]
[[Category:Triangulum]]
[[Category:Principal Galaxies Catalogue objects|073991]]