3C 273

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 {{convert|6|inch|adj=on}} amateur telescope.{{citation|work=Astronomy|title=Target acquired: Observe Quasar 3C 273|first=Richard |last=Talcott | date=November 17, 2023|url=https://www.astronomy.com/observing/hunting-quasar-3c-273/}} 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).{{cite web | url=http://hpiers.obspm.fr/icrs-pc/icrs/def_syst.html | title=Definition of ICRS Axes | author=International Earth Rotation & Reference Systems Service | access-date=11 January 2012}}

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.

Image:Quasar 3C 273.jpg'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. A luminosity distance of D_L = {{convert|749|Mpc|e9ly|1|abbr=off|lk=on}} may be calculated from z.{{cite journal | display-authors=6 | author=Uchiyama, Yasunobu | author2=Urry, C. Megan | author3=Cheung, C. C. | author4=Jester, Sebastian | author5=Van Duyne, Jeffrey | author6=Coppi, Paolo | author7=Sambruna, Rita M. | author8=Takahashi, Tadayuki | author9= Tavecchio, Fabrizio | author10=Maraschi, Laura | title=Shedding New Light on the 3C 273 Jet with the Spitzer Space Telescope | journal=The Astrophysical Journal | date=2006 | volume=648 | issue=2 | pages=910–921 | bibcode=2006ApJ...648..910U | doi=10.1086/505964|arxiv = astro-ph/0605530 | s2cid=119520309 }} Using parallax methods with the Very Large Telescope interferometer yields a distance estimate of {{val|1.80|0.32|0.28|u=Gly|fmt=commas}} ({{val|552|97|79|u=Mpc}}).

It is one of the most luminous quasars known, with an absolute magnitude of −26.7,{{Cite journal|title=The Quasi-Stellar Radio Sources 3C 48 and 3C 273| bibcode=1964ApJ...140....1G| journal=The Astrophysical Journal|year=1964 |doi = 10.1086/147889 |last1=Greenstein |first1=Jesse L. |last2=Schmidt |first2=Maarten |volume=140 |page=1 |s2cid=123147304 |doi-access=free }} meaning that if it were only as distant as Pollux (~10 parsecs) it would appear nearly as bright in the sky as the Sun.{{cite web | title=Best image of bright quasar 3C 273 | website=esahubble.org | date=November 18, 2013 | url=https://esahubble.org/images/potw1346a/ | access-date=2023-02-25 }} 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.Per the formula for comparing fluxes and magnitudes: $10^\{(4.83+26.7)/2.5\}=4.09*10^\{12\}$.

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. 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.{{Cite journal|doi=10.1038/290365a0|title=Superluminal expansion of quasar 3C273|date=1981|last1=Pearson|first1=T. J.|last2=Unwin|first2=S. C.|last3=Cohen|first3=M. H.|last4=Linfield|first4=R. P.|last5=Readhead|first5=A. C. S.|last6=Seielstad|first6=G. A.|last7=Simon|first7=R. S.|last8=Walker|first8=R. C.|journal=Nature|volume=290|issue=5805|pages=365|bibcode = 1981Natur.290..365P |s2cid=26508893 }}{{Cite journal|doi=10.1038/354374a0|title=Large-scale superluminal motion in the quasar 3C273|date=1991|last1=Davis|first1=R. J.|last2=Unwin|first2=S. C.|last3=Muxlow|first3=T. W. B.|journal=Nature|volume=354|issue=6352|pages=374|bibcode = 1991Natur.354..374D |s2cid=4271003 }}

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.{{cite journal | title=Jet-driven Galaxy-scale Gas Outflows in the Hyperluminous Quasar 3C 273 | last1=Husemann | first1=Bernd | last2=Bennert | first2=Vardha N. | last3=Jahnke | first3=Knud | last4=Davis | first4=Timothy A. | last5=Woo | first5=Jong-Hak | last6=Scharwächter | first6=Julia | last7=Schulze | first7=Andreas | last8=Gaspari | first8=Massimo | last9=Zwaan | first9=Martin A. | journal=The Astrophysical Journal | volume=879 | issue=2 | id=75 | date=July 2019 | page=75 | doi=10.3847/1538-4357/ab24bc | arxiv=1905.10387 | bibcode=2019ApJ...879...75H | s2cid=166227892 | doi-access=free }} The mass of its central SMBH has been measured to be {{val|886|187}} million solar masses through broad emission-line reverberation mapping.{{cite journal | display-authors=6 | author=Peterson, B. M. | author2=Ferrarese, L. | author3=Gilbert, K. M. | author4=Kaspi, S. | author5=Malkan, M. A. | author6=Maoz, D. | author7=Merritt, D. | author7-link=David Merritt | author8=Netzer, H. | author9=Onken, C. A. | author10=Pogge, R. W. | author11=Vestergaard, M. | author12=Wandel, A. | title=Central Masses of AGNs. II. | journal=The Astrophysical Journal | date=2004 | volume=613 | issue=2 | pages=682–699 | doi=10.1086/423269| bibcode=2004ApJ...613..682P|arxiv = astro-ph/0407299 | s2cid=16308360 }}

The quasar has a large-scale visible jet, which measures ~{{convert|200000|ly|kpc}} long, having an apparent size of 23″. 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. 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°.{{cite journal | title=An Oversized Magnetic Sheath Wrapping around the Parsec-scale Jet in 3C 273 | last1=Lisakov | first1=M. M. | last2=Kravchenko | first2=E. V. | last3=Pushkarev | first3=A. B. | last4=Kovalev | first4=Y. Y. | last5=Savolainen | first5=T. K. | last6=Lister | first6=M. L. | journal=The Astrophysical Journal | volume=910 | issue=1 | id=35 | date=March 2021 | page=35 | doi=10.3847/1538-4357/abe1bd | arxiv=2102.04563 | bibcode=2021ApJ...910...35L | s2cid=231855529 | doi-access=free }} An expanding cocoon of heated gas is being generated by the jet, which may be impacting an inclined disk of gas within the central {{val|6|u=kpc|p=~ }}.

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,{{cite journal | author=Bahcall, John N. | author2=Kirhakos, Sofia | author3=Saxe, David H. | author4=Schneider, Donald P. | title=Hubble Space Telescope Images of a Sample of 20 Nearby Luminous Quasars | journal=The Astrophysical Journal | date=1997 | volume=479 | issue=2 | pages=642–658 |arxiv=astro-ph/9611163 | bibcode=1997ApJ...479..642B | doi=10.1086/303926| s2cid=15318893 }} indicating a moderately flattened elliptical shape. The galaxy has an estimated mass of {{val|2|e=11|ul=solar mass|p=~ }}.{{cite journal | title=Kinematics of the Broad-line Region of 3C 273 from a 10 yr Reverberation Mapping Campaign | last1=Zhang | first1=Zhi-Xiang | last2=Du | first2=Pu | last3=Smith | first3=Paul S. | last4=Zhao | first4=Yulin | last5=Hu | first5=Chen | last6=Xiao | first6=Ming | last7=Li | first7=Yan-Rong | last8=Huang | first8=Ying-Ke | last9=Wang | first9=Kai | last10=Bai | first10=Jin-Ming | last11=Ho | first11=Luis C. | last12=Wang | first12=Jian-Min | journal=The Astrophysical Journal | volume=876 | issue=1 | id=49 | date=May 2019 | page=49 | doi=10.3847/1538-4357/ab1099 | arxiv=1811.03812 | bibcode=2019ApJ...876...49Z | s2cid=119403004 | doi-access=free }}

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,{{cite journal | author=Hazard, C. | author2=Mackey, M. B. | author3=Shimmins, A. J. | title=Investigation of the Radio Source 3C273 by the method of Lunar Occultations | journal=Nature | date=1963 | volume=197 | issue=4872 | pages=1037 | bibcode=1963Natur.197.1037H | doi=10.1038/1971037a0| s2cid=4270661 }} the radio source was quickly associated with an optical counterpart, an unresolved stellar object. In 1963, Maarten Schmidt{{cite journal | author=Schmidt, M.| title=3C 273 : A Star-Like Object with Large Red-Shift| journal=Nature| date=1963| volume=197| issue=4872| pages=1040| bibcode=1963Natur.197.1040S| doi=10.1038/1971040a0| doi-access=free}} and Bev Oke{{cite journal| author=Oke, J. B.| title=Absolute Energy Distribution in the Optical Spectrum of 3C 273| journal=Nature| date=1963| volume=197| issue=4872| pages=1040–1041| bibcode=1963Natur.197.1040O| doi=10.1038/1971040b0| s2cid=4269940}} 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, the process which gives rise to the X-ray emissions was still controversial as of 2006 when new observations were reported with the Spitzer Space Telescope.

• List of quasars

{{reflist}}

• [http://isdc.unige.ch/3c273/ 3C 273's Database at the INTEGRAL Science Data Centre (ESA)]
• [http://www.perseus.gr/Astro-DSO-QSO-3C273.htm Detailed CCD image of 3C 273 based on 30 min total exposure]
• [http://astro.neutral.org/imagehtml/20050408_3c273.html Amateur 3C 273 Redshift Measurement]
• [http://www.nightskyinfo.com/archive/3c273_quasar NightSkyInfo.com – 3C 273]
• [http://www.sky-map.org/?object=3C%20273&zoom=12&img_source=SDSS SKY-MAP.ORG SDSS image of 3C 273]
• [https://web.archive.org/web/20090123191313/http://www.aavso.org/vstar/vsots/spring05.shtml The Quasar 3C 273: Spring 2005 – Variable Star Of The Season AAVSO]
• {{WikiSky|z=12}}

{{Sky|12|29|06.7|+|02|03|09|2440000000}}

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