View source for Cygnus A

{{short description|Radio galaxy}}
{{Infobox Galaxy
| name = Cygnus A
| image = 3c405.jpg
| image_size = 300px
| epoch = [[J2000]]
| ra = {{RA|19|59|28.3566}}<ref name="ned">{{cite web
| work=NASA/IPAC Extragalactic Database
| title=Results for Cygnus A
| url=http://nedwww.ipac.caltech.edu/cgi-bin/objsearch?objname=Cygnus+A&extend=no
| access-date=2008-10-01}}</ref>
| dec = {{DEC|+40|44|02.096}}<ref name="ned" /><ref name="simbad">{{cite simbad
| title =NAME Cygnus A
| access-date =2016-02-29}}</ref>
| constellation name = [[Cygnus (constellation)|Cygnus]]
| z = 0.056075 ± 0.000067<ref name="ned" /><ref name="simbad" />
| dist_ly = {{Convert|232|Mpc|e6ly|abbr=unit}}<ref name=Graham2008/>
| type = E<ref name="ned" /><ref name="simbad" />
| appmag_v = 16.22<ref name="ned" /><ref name="simbad" />
| size_v = 0.549' × 0.457'<ref name="ned" /><ref name="simbad" />
| notes =
| names = [[Fourth Cambridge Survey|4C]] 40.40, [[Einstein Observatory|2E]] 4309, CYG A, W 57, BWE 1957+4035, [[NRAO]] 620, [[First Cambridge Catalogue of Radio Sources|1C]] 19.01, [[Quasar|QSO]] B1957+405, [[Third Cambridge Catalogue of Radio Sources|3C]] 405, [[1RXS]] J195928.7+404405, [[Third Cambridge Catalogue of Radio Sources|3C]] 405.0, [[2U (astronomical catalog)|2U]] 1957+40, [[Third Cambridge Catalogue of Radio Sources|3CR]] 405, [[Lyon-Meudon Extragalactic Database|LEDA]] 63932, [[4U (astronomical catalogue)|4U]] 1957+40, [[VV2000c]] J195928.3+404402, [[List of astronomical catalogues#D|DA]] 500, [[Morphological Catalogue of Galaxies|MCG]]+07-41-003, [[DB (astronomical catalog)|DB]] 117, [[Mills (astronomical catalog)|Mills]] 19+4, [[Atlas of Interacting Galaxies|VV]] 72,<ref name="ned" /> PGC 63932.
}}
'''Cygnus A''' ([[Third Cambridge Catalogue of Radio Sources|3C]] 405) is a [[radio galaxy]], one of the strongest [[astronomical radio source|radio sources]] in the sky. A concentrated radio source in Cygnus was discovered by [[Grote Reber]] in 1939. In 1946 [[James Stanley Hey|Stanley Hey]] and his colleague James Phillips identified that the source [[twinkling|scintillated]] rapidly, and must therefore be a compact object.<ref>{{cite journal | doi=10.1098/rspa.1948.0017 | title=An investigation of galactic radiation in the radio spectrum | journal=Proceedings of the Royal Society of London. Series A. Mathematical and Physical Sciences | year=1948 | volume=192 | issue=1030 | pages=425–445 | bibcode=1948RSPSA.192..425H | last1=Hey | first1=J. S. | last2=Parsons | first2=S. J. | last3=Phillips | first3=J. W. | s2cid=121054928 }}</ref> In 1951, Cygnus A, along with [[Cassiopeia A]], and [[Puppis A]] were the first "radio stars" identified with an optical source. Of these, Cygnus A became the first radio galaxy, the other two being [[nebula]]e inside the [[Milky Way]].<ref name=ApJ-1954-01>{{cite journal | doi=10.1086/145812 | title=Identification of the Radio Sources in Cassiopeia, Cygnus a, and Puppis A | year=1954 | last1=Baade | first1=W. | last2=Minkowski | first2=R. | journal=The Astrophysical Journal | volume=119 | page=206 | bibcode=1954ApJ...119..206B }}</ref> In 1953 [[Roger Clifton Jennison|Roger Jennison]] and [[Mrinal Kumar Das Gupta|M K Das Gupta]] showed it to be a double source.<ref>{{cite journal
| author1=Jennison, R.C.
| author2=Das Gupta, M.K.
| title=Fine Structure of the extra-terrestrial radio source Cygnus 1
| journal=Nature
| page=996
| year=1953
| volume=172
| issue=4387
| doi=10.1038/172996a0
| bibcode=1953Natur.172..996J
| s2cid=4251058
| url=http://ukads.nottingham.ac.uk/cgi-bin/nph-bib_query?bibcode=1953Natur.172..996J&amp;db_key=AST
| archive-url=https://web.archive.org/web/20190827000433/http://ukads.nottingham.ac.uk/cgi-bin/nph-bib_query?bibcode=1953Natur.172..996J&amp;db_key=AST
| url-status=dead
| archive-date=August 27, 2019
}}</ref> Like all radio galaxies, it contains an [[active galactic nucleus]]. The [[supermassive black hole]] at the core has a mass of {{Val|2.5e9|.7|ul=solar mass}}.<ref name=Graham2008>{{cite journal
| title=Populating the Galaxy Velocity Dispersion - Supermassive Black Hole Mass Diagram: A Catalogue of (Mbh, σ) Values
| last1=Graham | first1=Alister W.
| journal=Publications of the Astronomical Society of Australia
| volume=25 | issue=4 | pages=167–175 | date=November 2008
| doi=10.1071/AS08013 | bibcode=2008PASA...25..167G |arxiv = 0807.2549 | s2cid=89905 }}</ref>
Images of the galaxy in the [[Radio wave|radio]] portion of the [[electromagnetic spectrum]] show two jets protruding in opposite directions from the galaxy's center. These jets extend many times the width of the portion of the host galaxy which emits radiation at [[Visible spectrum|visible wavelengths]].<ref>{{cite web
| author=Strange, D
| title=The Radio Galaxy Cygnus "A"
| url=http://ourworld.compuserve.com/homepages/dstrange/cygnusa.htm
| access-date=2008-09-22
| url-status=dead
| archive-url=https://web.archive.org/web/20080725125333/http://ourworld.compuserve.com/homepages/dstrange/cygnusa.htm
| archive-date=July 25, 2008
}}</ref> At the ends of the jets are two lobes with "hot spots" of more intense radiation at their edges. These hot spots are formed when material from the jets collides with the surrounding [[Outer space|intergalactic medium]].<ref>{{cite web
|author1=Nemiroff, Robert |author-link1 = Robert J. Nemiroff |author2=Bonnell, Jerry | title= X-Ray Cygnus A
| work=Astronomy Picture of the Day
| date=2002-10-05
| url=http://www.sai.msu.su/apod/ap021005.html
| access-date=2008-09-22}}</ref>
In 2016, a radio [[transient astronomical event|transient]] was discovered 460 [[parsec]]s away from the center of Cygnus A. Between 1989 and 2016, the object, cospatial with a previously-known infrared source, exhibited at least an eightfold increase in radio [[flux density]], with comparable luminosity to the brightest known [[supernova]]. Due to the lack of measurements in the intervening years, the rate of brightening is unknown, but the object has remained at a relatively constant flux density since its discovery. The data are consistent with a [[binary black hole|second supermassive black hole]] orbiting the primary object, with the secondary having undergone a rapid accretion rate increase. The inferred orbital timescale is of the same order as the activity of the primary source, suggesting the secondary may be perturbing the primary and causing the outflows.<ref name="PerleyPerley2017">{{cite journal|last1=Perley|first1=D. A.|last2=Perley|first2=R. A.|last3=Dhawan|first3=V.|last4=Carilli|first4=C. L.|title=Discovery of a Luminous Radio Transient 460 pc from the Central Supermassive Black Hole in Cygnus A|journal=The Astrophysical Journal|volume=841|issue=2|year=2017|pages=117|issn=1538-4357|doi=10.3847/1538-4357/aa725b|arxiv = 1705.07901 |bibcode = 2017ApJ...841..117P |s2cid=54536121 |doi-access=free }}</ref>
== See also ==
* [[List of galaxies]]
* [[List of nearest galaxies]]
== References ==
<references/>
==Further reading==
* {{cite journal |bibcode=1994Natur.367..713H|title=X-ray emission from the radio hotspots of Cygnus A |last1=Harris |first1=D. E. |last2=Carilli |first2=C. L. |last3=Perley |first3=R. A. |journal=Nature |year=1994 |volume=367 |issue=6465 |page=713 |doi=10.1038/367713a0 |s2cid=4352349 }}
*{{cite web
| title=Cygnus A
| work=SIMBAD Astronomical Database
| url=http://simbad.u-strasbg.fr/simbad/sim-id?protocol=html&Ident=Cygnus+A&NbIdent=1&Radius=2&Radius.unit=arcmin&submit=submit+id}}
*{{cite web
| author=Blanco, Philip
| title=The powerful radio galaxy Cygnus A
| date=1997-02-07
| url=http://mamacass.ucsd.edu/people/pblanco/cyga.html
| url-status=dead
| archive-url=https://archive.today/20120210140951/http://mamacass.ucsd.edu/people/pblanco/cyga.html
| archive-date=2012-02-10
}}
*{{cite web |last1=Tuesday |first1=Alison Klesman |date=May 2017 |title=A familiar galaxy with a new surprise: Two supermassive black holes |url=https://astronomy.com/news/2017/05/galaxy-with-two-supermassive-black-holes |website=Astronomy.com |language=en}}
== External links ==
{{commonscat}}
*[http://simbad.u-strasbg.fr/sim-id.pl?protocol=html&Ident=cygnus+a&NbIdent=1&Radius=10&Radius.unit=arcmin&CooFrame=FK5&CooEpoch=2000&CooEqui=2000&output.max=all&o.catall=on&output.mesdisp=N&Bibyear1=1983&Bibyear2=2005&Frame1=FK5&Frame2=FK4&Frame3=G&Equi1=2000.0&Equi2=1950.0&Equi3=2000.0&Epoch1=2000.0&Epoch2=1950.0&Epoch3=2000.0 Information about Cygnus A] from SIMBAD.
*[http://hubblesite.org/newscenter/archive/releases/1994/1994/42/text/ Hubble Uncovers a Hidden Quasar in a Nearby Galaxy (Cygnus A)]
*[https://www.g4fas.net/1998-07-07-Cygnus-A-night-of-nights.html A primitive transit recording (7 July 1998) of Cygnus A by English radio amateur Geoff Royle G4FAS]
{{Stars of Cygnus}}
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[[Category:3C objects|405.0]]
[[Category:Cygnus (constellation)]]
[[Category:Radio galaxies]]
[[Category:Quasars]]
[[Category:Astronomical objects discovered in 1939]]