3C 273
Quasar 3C 273 taken by HST[1]
Observation data (Epoch J2000)
Right ascension12h 29m 06.7s[2]
Declination+02° 03′ 09″[2]
Redshift0.158339 ± 0.000067[2]
Distance2.443 Gly (749 Mpc)[3][4] (luminosity distance)
)[5] (parallax distance)
TypeBlazar; Sy1[2]
Apparent magnitude (V)12.9[2]
Notable featuresoptically brightest quasar, first spectrum of a quasar
Other designations
PGC 41121[2] and HIP 60936
See also: Quasar, List of quasars

3C 273 is a quasar located at the center of a giant elliptical galaxy in the constellation of Virgo. It was the first quasar ever to be identified and is the visually brightest quasar in the sky as seen from Earth, with an apparent visual magnitude of 12.9.[2] The derived distance to this object is 749 megaparsecs (2.4 billion light-years). The mass of its central supermassive black hole is approximately 886 million times the mass of the Sun.


3C 273 is visible from March to July in both the northern and southern hemispheres. Situated in the Virgo constellation, it is bright enough to be observed by eye with a 6-inch (150 mm) amateur telescope.[6] Due in part to its radio luminosity and its discovery as the first identified quasar, 3C 273's right ascension in the Fifth Fundamental Catalog (FK5) is used to standardize the positions of 23 extragalactic radio sources used to define the International Celestial Reference System (ICRS).[7]

Given its distance from Earth and visual magnitude, 3C 273 is the most distant celestial object average amateur astronomers are likely to see through their telescopes.


3C 273 as imaged by the Hubble Space Telescope's Advanced Camera for Surveys. Light from the bright quasar nucleus is blocked by a coronagraph so that the surrounding host galaxy can be more easily seen. Credit: NASA/ESA

This is the optically brightest quasar in the sky from Earth with an apparent visual magnitude of ~12.9, and one of the closest with a redshift, z, of 0.158.[8] A luminosity distance of DL = 749 megaparsecs (2.4 billion light-years) may be calculated from z.[4] Using parallax methods with the Very Large Telescope interferometer yields a distance estimate of 1.80+0.32

It is one of the most luminous quasars known, with an absolute magnitude of −26.7,[9] meaning that if it were only as distant as Pollux (~10 parsecs) it would appear nearly as bright in the sky as the Sun.[10] Since the Sun's absolute magnitude is 4.83, it means that the quasar is over 4 trillion times more luminous than the Sun at visible wavelengths.[11]

The luminosity of 3C 273 is variable at nearly every wavelength from radio waves to gamma rays on timescales of a few days to decades. Polarization with coincident orientation has been observed with radio, infrared, and optical light being emitted from a large-scale jet; these emissions are therefore almost certainly synchrotron in nature.[4] The radiation is created by a jet of charged particles moving at relativistic speeds. VLBI radio observations of 3C 273 have revealed proper motion of some of the radio emitting regions, further suggesting the presence of relativistic jets of material.[12][13]

This is a prototype of an Active Galactic Nucleus, demonstrating that the energy is being produced through accretion by a supermassive black hole (SMBH). No other astrophysical source can produce the observed energy.[14] The mass of its central SMBH has been measured to be 886±187 million solar masses through broad emission-line reverberation mapping.[15]

Large-scale jet

The quasar has a large-scale visible jet, which measures ~200,000 light-years (61 kpc) long, having an apparent size of 23″.[4] Such jets are believed to be created by the interaction of the central black hole and the accretion disk. In 1995, optical imaging of the jet using the Hubble Space Telescope revealed a structured morphology evidenced by repeated bright knots interlaced by areas of weak emission.[4] The viewing angle of the jet is about 6° as seen from Earth. The jet was observed to abruptly change direction by an intrinsic angle of 2° in 2003, which is larger than the jet's intrinsic opening angle of 1.1°.[16] An expanding cocoon of heated gas is being generated by the jet, which may be impacting an inclined disk of gas within the central ~ 6 kpc.[14]

Host galaxy

3C 273 lies at the center of a giant elliptical galaxy with an apparent magnitude of 16 and an apparent size of 29 arcseconds. The morphological classification of the host galaxy is E4,[17] indicating a moderately flattened elliptical shape. The galaxy has an estimated mass of ~ 2×1011 M.[18]


The name signifies that it was the 273rd object (ordered by right ascension) of the Third Cambridge Catalog of Radio Sources (3C), published in 1959. After accurate positions were obtained using lunar occultation by Cyril Hazard at the Parkes Radio Telescope,[19] the radio source was quickly associated with an optical counterpart, an unresolved stellar object. In 1963, Maarten Schmidt[8] and Bev Oke[20] published a pair of papers in Nature reporting that 3C 273 has a substantial redshift of 0.158, placing it several billion light-years away.

Prior to the discovery of 3C 273, several other radio sources had been associated with optical counterparts, the first being 3C 48. Also, many active galaxies had been misidentified as variable stars, including the famous BL Lac, W Com and AU CVn. However, it was not understood what these objects were, since their spectra were unlike those of any known stars. Its spectrum did not resemble that of any normal stars with typical stellar elements. 3C 273 was the first object to be identified as a quasar—an extremely luminous object at an astronomical distance.

3C 273 is a radio-loud quasar, and was also one of the first extragalactic X-ray sources discovered in 1970. However, even to this day, the process which gives rise to the X-ray emissions is controversial.[4]

See also


  1. ^ "Best image of bright quasar 3C 273". ESA/Hubble Picture of the Week. Retrieved 20 November 2013.
  2. ^ a b c d e f g "NASA/IPAC Extragalactic Database". Results for 3C 273. Retrieved 2006-10-26.
  3. ^ "3C 273". XJET: X-Ray Emission from Extragalactic Radio Jets. 2008-01-11. Retrieved 2010-04-05.
  4. ^ a b c d e f Uchiyama, Yasunobu; Urry, C. Megan; Cheung, C. C.; Jester, Sebastian; Van Duyne, Jeffrey; Coppi, Paolo; et al. (2006). "Shedding New Light on the 3C 273 Jet with the Spitzer Space Telescope". The Astrophysical Journal. 648 (2): 910–921. arXiv:astro-ph/0605530. Bibcode:2006ApJ...648..910U. doi:10.1086/505964. S2CID 119520309.
  5. ^ a b Wang, Jian-Min; Songsheng, Yu-Yang; Li, Yan-Rong; Du, Pu; Zhang, Zhi-Xiang (January 2020). "A parallax distance to 3C 273 through spectroastrometry and reverberation mapping". Nature Astronomy. 4 (5): 517–525. arXiv:1906.08417. Bibcode:2020NatAs...4..517W. doi:10.1038/s41550-019-0979-5. S2CID 256707018.
  6. ^ Talcott, Richard (November 17, 2023), "Target acquired: Observe Quasar 3C 273", Astronomy
  7. ^ International Earth Rotation & Reference Systems Service. "Definition of ICRS Axes". Retrieved 11 January 2012.
  8. ^ a b Schmidt, M. (1963). "3C 273 : A Star-Like Object with Large Red-Shift". Nature. 197 (4872): 1040. Bibcode:1963Natur.197.1040S. doi:10.1038/1971040a0.
  9. ^ Greenstein, Jesse L.; Schmidt, Maarten (1964). "The Quasi-Stellar Radio Sources 3C 48 and 3C 273". The Astrophysical Journal. 140: 1. Bibcode:1964ApJ...140....1G. doi:10.1086/147889. S2CID 123147304.
  10. ^ "Best image of bright quasar 3C 273". esahubble.org. November 18, 2013. Retrieved 2023-02-25.
  11. ^ Per the formula for comparing fluxes and magnitudes: .
  12. ^ Pearson, T. J.; Unwin, S. C.; Cohen, M. H.; Linfield, R. P.; Readhead, A. C. S.; Seielstad, G. A.; Simon, R. S.; Walker, R. C. (1981). "Superluminal expansion of quasar 3C273". Nature. 290 (5805): 365. Bibcode:1981Natur.290..365P. doi:10.1038/290365a0. S2CID 26508893.
  13. ^ Davis, R. J.; Unwin, S. C.; Muxlow, T. W. B. (1991). "Large-scale superluminal motion in the quasar 3C273". Nature. 354 (6352): 374. Bibcode:1991Natur.354..374D. doi:10.1038/354374a0. S2CID 4271003.
  14. ^ a b Husemann, Bernd; Bennert, Vardha N.; Jahnke, Knud; Davis, Timothy A.; Woo, Jong-Hak; Scharwächter, Julia; Schulze, Andreas; Gaspari, Massimo; Zwaan, Martin A. (July 2019). "Jet-driven Galaxy-scale Gas Outflows in the Hyperluminous Quasar 3C 273". The Astrophysical Journal. 879 (2): 75. arXiv:1905.10387. Bibcode:2019ApJ...879...75H. doi:10.3847/1538-4357/ab24bc. S2CID 166227892. 75.
  15. ^ Peterson, B. M.; Ferrarese, L.; Gilbert, K. M.; Kaspi, S.; Malkan, M. A.; Maoz, D.; et al. (2004). "Central Masses of AGNs. II". The Astrophysical Journal. 613 (2): 682–699. arXiv:astro-ph/0407299. Bibcode:2004ApJ...613..682P. doi:10.1086/423269. S2CID 16308360.
  16. ^ Lisakov, M. M.; Kravchenko, E. V.; Pushkarev, A. B.; Kovalev, Y. Y.; Savolainen, T. K.; Lister, M. L. (March 2021). "An Oversized Magnetic Sheath Wrapping around the Parsec-scale Jet in 3C 273". The Astrophysical Journal. 910 (1): 35. arXiv:2102.04563. Bibcode:2021ApJ...910...35L. doi:10.3847/1538-4357/abe1bd. S2CID 231855529. 35.
  17. ^ Bahcall, John N.; Kirhakos, Sofia; Saxe, David H.; Schneider, Donald P. (1997). "Hubble Space Telescope Images of a Sample of 20 Nearby Luminous Quasars". The Astrophysical Journal. 479 (2): 642–658. arXiv:astro-ph/9611163. Bibcode:1997ApJ...479..642B. doi:10.1086/303926. S2CID 15318893.
  18. ^ Zhang, Zhi-Xiang; Du, Pu; Smith, Paul S.; Zhao, Yulin; Hu, Chen; Xiao, Ming; Li, Yan-Rong; Huang, Ying-Ke; Wang, Kai; Bai, Jin-Ming; Ho, Luis C.; Wang, Jian-Min (May 2019). "Kinematics of the Broad-line Region of 3C 273 from a 10 yr Reverberation Mapping Campaign". The Astrophysical Journal. 876 (1): 49. arXiv:1811.03812. Bibcode:2019ApJ...876...49Z. doi:10.3847/1538-4357/ab1099. S2CID 119403004. 49.
  19. ^ Hazard, C.; Mackey, M. B.; Shimmins, A. J. (1963). "Investigation of the Radio Source 3C273 by the method of Lunar Occultations". Nature. 197 (4872): 1037. Bibcode:1963Natur.197.1037H. doi:10.1038/1971037a0. S2CID 4270661.
  20. ^ Oke, J. B. (1963). "Absolute Energy Distribution in the Optical Spectrum of 3C 273". Nature. 197 (4872): 1040–1041. Bibcode:1963Natur.197.1040O. doi:10.1038/1971040b0. S2CID 4269940.