Quasar

For other uses, see Quasar (disambiguation). "Quasi-stellar object" redirects here. Not to be confused with Quasi-star or Quaoar.
Artist's rendering of the accretion disc in ULAS J1120+0641, a very distant quasar powered by a supermassive black hole with a mass two billion times that of the Sun[1]
The Chandra X-ray image is of the quasar PKS 1127-145, a highly luminous source of X-rays and visible light about 10 billion light-years from Earth. An enormous X-ray jet extends at least a million light-years from the quasar. Image is 60 arcseconds on a side. RA 11h 30m 7.10s Dec −14° 49' 27" in Crater. Observation date: May 28, 2000. Instrument: ACIS

A quasar (/ˈkweɪzɑːr/ KWAY-zar) is an extremely luminous active galactic nucleus (AGN). It is sometimes known as a quasi-stellar object, abbreviated QSO. The emission from an AGN is caused by a supermassive black hole with a mass ranging from millions to tens of billions of solar masses, surrounded by a gaseous accretion disc. Gas in the disc falling towards the black hole heats up and releases energy in the form of electromagnetic radiation. The radiant energy of quasars is enormous; the luminosities alone may be thousands of times greater than that of a galaxy such as the Milky Way.[2][3] Quasars are usually categorized as a subclass of the more general category of AGN. The redshifts of quasars are of cosmological origin.[4]

The term quasar originated as a contraction of "quasi-stellar [star-like] radio source"—because they were first identified during the 1950s as sources of radio-wave emission of unknown physical origin—and when identified in photographic images at visible wavelengths, they resembled faint, star-like points of light. High-resolution images of quasars, particularly from the Hubble Space Telescope, have shown that quasars occur in the centers of galaxies, and that some host galaxies are strongly interacting or merging galaxies.[5] As with other categories of AGN, the observed properties of a quasar depend on many factors, including the mass of the black hole, the rate of gas accretion, the orientation of the accretion disc relative to the observer, the presence or absence of a jet, and the degree of obscuration by gas and dust within the host galaxy.

About a million quasars have been identified with reliable spectroscopic redshifts,[6] and between 2-3 million identified in photometric catalogs.[7][8] The nearest known quasar is about 600 million light-years from Earth, while the record for the most distant known quasar is 31.7 billion light-years away.[9][10]

Quasar discovery surveys have shown that quasar activity was more common in the distant past; the peak epoch was approximately 10 billion years ago.[11] Concentrations of multiple quasars are known as large quasar groups and may constitute some of the largest known structures in the universe if the observed groups are good tracers of mass distribution.

  1. ^ "Most Distant Quasar Found". ESO Science Release. Retrieved 4 July 2011.
  2. ^ Wu, Xue-Bing; et al. (2015). "An ultraluminous quasar with a twelve-billion-solar-mass black hole at redshift 6.30". Nature. 518 (7540): 512–515. arXiv:1502.07418. Bibcode:2015Natur.518..512W. doi:10.1038/nature14241. PMID 25719667. S2CID 4455954.
  3. ^ Frank, Juhan; King, Andrew; Raine, Derek J. (February 2002). Accretion Power in Astrophysics (Third ed.). Cambridge, UK: Cambridge University Press. Bibcode:2002apa..book.....F. ISBN 0521620538.
  4. ^ "Quasars and Active Galactic Nuclei". ned.ipac.caltech.edu. Retrieved 2020-08-31.
  5. ^ Bahcall, J. N.; et al. (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.
  6. ^ "Million Quasars Catalog, Version 8 (2 August 2023)". MILLIQUAS. 2023-08-02. Retrieved 2023-11-20.
  7. ^ Shu, Yiping; Koposov, Sergey E; Evans, N Wyn; Belokurov, Vasily; McMahon, Richard G; Auger, Matthew W; Lemon, Cameron A (2019-09-05). "Catalogues of active galactic nuclei from Gaia and unWISE data". Monthly Notices of the Royal Astronomical Society. 489 (4). Oxford University Press (OUP): 4741–4759. arXiv:1909.02010. doi:10.1093/mnras/stz2487. ISSN 0035-8711.
  8. ^ Storey-Fisher, Kate; Hogg, David W.; Rix, Hans-Walter; Eilers, Anna-Christina; Fabbian, Giulio; Blanton, Michael; Alonso, David (2024). "Quaia, the Gaia-unWISE Quasar Catalog: An All-Sky Spectroscopic Quasar Sample". AAS Journals. 964 (1): 69. arXiv:2306.17749. Bibcode:2024ApJ...964...69S. doi:10.3847/1538-4357/ad1328.
  9. ^ "APOD: 2023 November 10 - UHZ1: Distant Galaxy and Black Hole". apod.nasa.gov. Retrieved 2023-11-10.
  10. ^ Whalen, Daniel J.; Latif, Muhammad A.; Mezcua, Mar (2023-10-01). "Radio Emission From a z = 10.1 Black Hole in UHZ1". The Astrophysical Journal. 956 (2): 133. arXiv:2308.03837. Bibcode:2023ApJ...956..133W. doi:10.3847/1538-4357/acf92c. ISSN 0004-637X.
  11. ^ Schmidt, Maarten; Schneider, Donald; Gunn, James (1995). "Spectroscopic CCD Surveys for Quasars at Large Redshift. IV. Evolution of the Luminosity Function from Quasars Detected by Their Lyman-Alpha Emission". The Astronomical Journal. 110: 68. Bibcode:1995AJ....110...68S. doi:10.1086/117497.