Editing Quasar (section)

=== Early observations (1960s and earlier) ===
The first quasars ([[3C 48]] and [[3C 273]]) were discovered in the late 1950s, as radio sources in all-sky radio surveys.<ref name="Shields">{{cite journal |last1=Shields |first1=Gregory A. |title=A Brief History of Active Galactic Nuclei |journal=The Publications of the Astronomical Society of the Pacific |date=1999 |volume=111 |issue=760 |pages=661–678 |access-date=3 October 2014 |url=http://ned.ipac.caltech.edu/level5/Sept04/Shields/Shields3.html |doi=10.1086/316378 |arxiv=astro-ph/9903401 |bibcode=1999PASP..111..661S |s2cid=18953602 }}</ref><ref>{{cite web |title=Our Activities |url=http://www.esa.int/Our_Activities/Space_Science/18_June/(print) |publisher=[[European Space Agency]] |access-date=3 October 2014}}</ref><ref>{{Cite journal |last1=Matthews |first1=Thomas A. |author-link=Thomas A. Matthews |last2=Sandage |first2=Allan R. |author-link2=Allan Sandage |date=July 1963 |title=Optical Identification of 3c 48, 3c 196, and 3c 286 with Stellar Objects. |journal=The Astrophysical Journal |language=en |volume=138 |pages=30 |bibcode=1963ApJ...138...30M |doi=10.1086/147615 |issn=0004-637X |doi-access=free}}</ref><ref>{{cite book |url=https://books.google.com/books?id=W-cbw-QdcHUC&pg=PA237 |title=Physics: Imagination and Reality |isbn=9789971509293 |last1=Wallace |first1=Philip Russell |year=1991|publisher=World Scientific }}</ref> They were first noted as radio sources with no corresponding visible object. Using small telescopes and the [[Lovell Telescope]] as an [[Interferometry|interferometer]], they were shown to have a very small angular size.<ref name="jbo">{{cite web |url=http://www.jb.man.ac.uk/public/story/mk1quasars.html |title=The MKI and the discovery of Quasars |publisher=[[Jodrell Bank Observatory]] |access-date=2006-11-23}}</ref> By 1960, hundreds of these objects had been recorded and published in the [[Third Cambridge Catalogue]] while astronomers scanned the skies for their optical counterparts. In 1963, a definite identification of the radio source [[3C 48]] with an optical object was published by [[Allan Sandage]] and [[Thomas A. Matthews]]. Astronomers had detected what appeared to be a faint blue star at the location of the radio source and obtained its spectrum, which contained many unknown broad emission lines. The anomalous spectrum defied interpretation.

British-Australian astronomer [[John Gatenby Bolton|John Bolton]] made many early observations of quasars, including a breakthrough in 1962. Another radio source, [[3C 273]], was predicted to undergo five [[occultation]]s by the [[Moon]]. Measurements taken by [[Cyril Hazard]] and John Bolton during one of the occultations using the [[Parkes Radio Telescope]] allowed [[Maarten Schmidt]] to find a visible counterpart to the radio source and obtain an [[optical spectrum]] using the {{convert|200|in|m|adj=on}} [[Hale Telescope]] on [[Palomar Mountain|Mount Palomar]]. This spectrum revealed the same strange emission lines. Schmidt was able to demonstrate that these were likely to be the ordinary [[spectral line]]s of hydrogen redshifted by 15.8%, at the time, a high redshift (with only a handful of much fainter galaxies known with higher redshift). If this was due to the physical motion of the "star", then 3C 273 was receding at an enormous velocity, around {{val|47,000|fmt=commas|u=km/s}}, far beyond the speed of any known star and defying any obvious explanation.<ref name="schmidt1963" /> Nor would an extreme velocity help to explain 3C 273's huge radio emissions. If the redshift was cosmological (now known to be correct), the large distance implied that 3C 273 was far more luminous than any galaxy, but much more compact. Also, 3C 273 was bright enough to detect on archival photographs dating back to the 1900s; it was found to be variable on yearly timescales, implying that a substantial fraction of the light was emitted from a region less than 1&nbsp;light-year in size, tiny compared to a galaxy.

Although it raised many questions, Schmidt's discovery quickly revolutionized quasar observation. The strange spectrum of [[3C 48]] was quickly identified by Schmidt, Greenstein and Oke as [[hydrogen]] and [[magnesium]] redshifted by 37%. Shortly afterwards, two more quasar spectra in 1964 and five more in 1965 were also confirmed as ordinary light that had been redshifted to an extreme degree.<ref name="Caltech_p3">{{Cite web |last=Shields |first=Gregory A. |date=1999 |title=A Brief History of AGN. 3.&nbsp;The Discovery Of Quasars |url=http://ned.ipac.caltech.edu/level5/Sept04/Shields/Shields3.html |website=[[California Institute of Technology]]}}</ref> While the observations and redshifts themselves were not doubted, their correct interpretation was heavily debated, and Bolton's suggestion that the radiation detected from quasars were ordinary [[spectral line]]s from distant highly redshifted sources with extreme velocity was not widely accepted at the time.