View source for Coma Cluster

{{Short description|Cluster of galaxies in the constellation Coma Berenices}}
{{distinguish|Coma Star Cluster}}
{{Galaxy cluster
| name = Coma Cluster
| image = [[Image:coma_cluster_leo.jpg|290px]]
| caption = Coma cluster of galaxies photographed by an amateur

| epoch = [[Epoch (astronomy)#Julian years and J2000|J2000]]
| ra = {{RA|12|59|48.7}}<ref name="NED">{{cite web
  | title = NASA/IPAC Extragalactic Database
  | work = Results for Abell 1656
  | url = http://ned.ipac.caltech.edu/cgi-bin/nph-objsearch?objname=Abell+1656&extend=no
  | access-date = 2006-09-19}}</ref>
| dec = {{DEC|+27|58|50}}<ref name="NED"/>
| constellation = [[Coma Berenices]]
| member_no = > 1000<ref name="chandra"/><ref name="nasafocuscoma"/>
| brightest_member = [[NGC 4874]] and [[NGC 4889]] 
| richness = 2<ref name="ACO">{{cite journal
 | last1 = Abell
 | first1 = George O.
 | author-link1 = George O. Abell
 | last2 = Corwin
 | first2 = Harold G. Jr.
 | author-link2 = Harold G. Corwin
 | last3 = Olowin
 | first3 = Ronald P.
 | author-link3 = Ronald P. Olowin
 | date = May 1989
 | title = A catalog of rich clusters of galaxies
 | journal = Astrophysical Journal Supplement Series
 | volume = 70
 | issue = May 1989
 | pages = 1–138
 | issn = 0067-0049
 | bibcode = 1989ApJS...70....1A
 | doi = 10.1086/191333
 | doi-access = free
 }}</ref>
| bmtype = II<ref name="ACO" />
| velocity_dispersion = 1,000 km/s<ref name="Struble 1999">{{cite journal
 | last1 = Struble
 | first1 = Mitchell F.
 | last2 = Rood
 | first2 = Herbert J.
 | date = November 1999
 | title = A Compilation of Redshifts and Velocity Dispersions for ACO Clusters
 | journal = The Astrophysical Journal Supplement Series
 | volume = 125
 | issue = 1
 | pages = 35–71
 | location = Chicago, Illinois, USA
 | publisher = [[The University of Chicago Press]]
 | bibcode = 1999ApJS..125...35S
 | doi = 10.1086/313274
 | doi-access = free
 }}</ref>
| redshift = 0.0231 (6 925 km/s)<ref name="NED" />
| distance = {{convert|102.975|Mpc|Mly|0|abbr=on|lk=on}} for {{hub|0.705}}<ref name="NED" />
| temperature = 8–9 [[electron volt|keV]]<ref name="Sato">Section 4 of {{cite journal
 | last1 = Sato
 | first1 = Takuya
 | last2 = Matsushita
 | first2 = Kyoko
 | last3 = Ota, Naomi; Sato, Kosuke; Nakazawa, Kazuhiro; Sarazin, Craig L.
 | date = November 2011
 | title = Suzaku Observations of Iron K-Lines from the Intracluster Medium of the Coma Cluster
 | journal = Publications of the Astronomical Society of Japan
 | volume = 63
 | issue = SP3
 | pages = S991–S1007
 | arxiv = 1109.0154
 | bibcode = 2011PASJ...63S.991S
 | access-date = March 12, 2012
 | url = http://pasj.asj.or.jp/v63/sp3/63s345/63s345.pdf
 | doi=10.1093/pasj/63.sp3.s991
}}</ref>
| mass = ~7{{e|14}}<ref>{{cite journal
  | last1 = Gavazzi
  | first1 = R.
  | last2 = Adami
  | first2 = C.
  | last3 = Durret
  | first3 = F.
  | last4 = Cuillandre
  | first4 = J.-C.
  | last5 = Ilbert
  | first5 = O.
  | last6 = Mazure
  | first6 = A.
  | last7 = Pelló
  | first7 = R.
  | last8 = Ulmer
  | first8 = M.P.
  | date = May 2009
  | title = A weak lensing study of the Coma cluster
  | journal = [[Astronomy and Astrophysics]]
  | volume = 498
  | issue = 2
  | pages = L33–L36
  | bibcode = 2009A&A...498L..33G
  | doi = 10.1051/0004-6361/200911841
  |arxiv = 0904.0220 | s2cid = 15418452
 }}</ref>
| luminosity = 
| flux = (319.20 ± 2.6%){{e|-12}} [[erg]] s<sup>−1</sup> cm<sup>−2</sup><ref name="NED" /> (0.1–2.4 [[electron volt|keV]])<ref name="NED" />
| other_names = [[Abell catalogue|Abell]] 1656<ref name="NED" />
}}

The '''Coma Cluster''' ('''Abell 1656''') is a large [[galaxy cluster|cluster of galaxies]] that contains over 1,000 identified galaxies.<ref name="chandra">{{cite web
 |title       = Chandra/Field Guide to X-ray Sources
 |work        = Coma Cluster
 |url         = http://chandra.harvard.edu/xray_sources/coma/
 |access-date  = 2008-06-16
 |archive-url  = https://web.archive.org/web/20080421215423/http://chandra.harvard.edu/xray_sources/coma/
 |archive-date = April 21, 2008
 
}} 
</ref><ref name="nasafocuscoma">{{cite web
 |title       = NASA / Focus on the Coma Cluster
 |url         = http://imagine.gsfc.nasa.gov/docs/features/objects/coma.html
 |access-date  = 2008-06-16
 
 |archive-url  = https://web.archive.org/web/20080530151953/http://imagine.gsfc.nasa.gov/docs/features/objects/coma.html
 |archive-date = 2008-05-30
}}</ref> Along with the [[Leo Cluster]] (Abell 1367), it is one of the two major clusters comprising the [[Coma Supercluster]].<ref>{{Cite web|title=The Coma Supercluster|url=http://www.atlasoftheuniverse.com/superc/com.html}}</ref> It is located in and takes its name from the constellation [[Coma Berenices]].

The cluster's mean distance from [[Earth]] is 99 [[Parsec|Mpc]] (321&nbsp;million [[light year]]s).<ref name="nasafocuscoma"/><ref name="IPAC">{{cite web |title=2MASS Atlas Image Gallery: Galaxy Groups and Clusters |publisher=Infrared Processing and Analysis Center |url=http://www.ipac.caltech.edu/2mass/gallery/images_galcl.html |access-date=2010-05-02}}</ref><ref>{{cite encyclopedia | last = Colless | first = M | editor = P Murdin | encyclopedia = Encyclopedia of Astronomy and Astrophysics | title = Coma Cluster | url = http://eaa.iop.org/abstract/0333750888/2600 | access-date = 2006-10-08 | date = 2001 | publisher = Bristol Institute of Physics publishing }}{{dead link|date=August 2017 |bot=InternetArchiveBot |fix-attempted=yes }}</ref> Its ten brightest spiral galaxies have [[apparent magnitude]]s of 12–14 that are observable with amateur telescopes larger than 20&nbsp;cm.<ref>{{cite web
  | title = ScienceNet – Astronomy & Space Science – Observatories/ Telescopes – Question No. 13490
  | author = Singapore Science Centre
  | archive-url = https://web.archive.org/web/20051111151435/http://www.science.edu.sg/ssc/detailed.jsp?artid=1950&type=6&root=6&parent=6&cat=66
  | archive-date = 2005-11-11
  | access-date = 2012-02-25
| url = http://www.science.edu.sg/ssc/detailed.jsp?artid=1950&type=6&root=6&parent=6&cat=66
  }}</ref> The central region is dominated by two supergiant [[elliptical galaxy|elliptical galaxies]]: [[NGC 4874]] and [[NGC 4889]].<ref>{{cite journal 
| author = Conselice, Christopher J., Gallagher, John S., III 
| title = Galaxy aggregates in the Coma cluster 
| journal = [[Monthly Notices of the Royal Astronomical Society]] 
| date = 1998 
| volume = 297 
| issue = 2 
| pages = L34–L38 
| doi = 10.1046/j.1365-8711.1998.01717.x
| doi-access = free 
| arxiv = astro-ph/9801160 
| bibcode = 1998MNRAS.297L..34C 
| s2cid = 14908115 
}}</ref> The cluster is within a few degrees of the north galactic pole on the sky. Most of the galaxies that inhabit the central portion of the Coma Cluster are ellipticals. Both dwarf and giant ellipticals are found in abundance in the Coma Cluster.<ref>[http://newswise.com/articles/view/541574/ Newswise: Hubble's Sweeping View of the Coma Cluster of Galaxies] Retrieved on June 11, 2008.</ref>

==Cluster members==
[[File:Wading through water.jpg|thumb|left|Tails in [[spiral galaxy]] [[D100 (Galaxy)|D100]], found in the Coma Cluster, are created by ram-pressure stripping.<ref>{{cite web |title=Wading through water |url=https://www.spacetelescope.org/images/potw1904a/ |website=www.spacetelescope.org |access-date=28 January 2019 |language=en}}</ref><ref>{{Cite journal|last=Cramer|first=William J.|display-authors=et al.|date=Jan 2019|title=Spectacular Hubble Space Telescope Observations of the Coma Galaxy D100 and Star Formation in Its Ram Pressure–stripped Tail |journal=The Astrophysical Journal |volume=870|issue=2|page=2|doi=10.3847/1538-4357/aaefff|arxiv=1811.04916|bibcode=2019ApJ...870...63C|s2cid=119218554 |doi-access=free }}</ref>]]

As is usual for clusters of this richness, the galaxies are overwhelmingly elliptical and [[S0 galaxy|S0 galaxies]], with only a few spirals of younger age, and many of them probably near the outskirts of the cluster.

The full extent of the cluster was not understood until it was more thoroughly studied in the 1950s by astronomers at [[Mount Palomar Observatory]], although many of the individual galaxies in the cluster had been identified previously.<ref>{{cite journal
| last1 = Zwicky
| first1 = Fritz
| author-link1 = Fritz Zwicky
|date=October 1937
| title = On the Masses of Nebulae and of Clusters of Nebulae
| journal = [[Astrophysical Journal]]
| volume = 86
| issue = 3
| pages = 217–246
| bibcode = 1937ApJ....86..217Z
| doi = 10.1086/143864
| doi-access = free
}}</ref><ref>{{cite journal
| last1 = Shapley
| first1 = Harlow
| author-link1 = Harlow Shapley
|date=July 1934
| title = A Photometric Investigation of Wolf's Cluster of Nebulae in Coma
| journal = Harvard College Observatory Bulletin
|volume=896
| pages = 3–12
| location = Cambridge, MA, USA
| bibcode = 1934BHarO.896....3S
}}</ref><ref>{{cite journal
| last1 = Wallenquist
| first1 = Å.
| date = 1933
| title = On the space distribution of the nebulae in the Coma Cluster
| journal = Annalen V.d. Bosscha-Sterrenwacht (Miscellaneous Papers (Observatorium Bosscha))
| volume = 4
| issue = 6
| pages = 73–77
| location = France
| publisher = Bandoeng : Gebrs. Kleijne
| bibcode = 1933AnBos...4...73W
}}</ref>

==Dark matter==
The Coma Cluster is one of the first places where observed gravitational anomalies were considered to be indicative of unobserved mass. In 1933 [[Fritz Zwicky]] showed that the galaxies of the Coma Cluster were moving too fast for the cluster to be bound together by the visible matter of its galaxies.  Though the idea of dark matter would not be accepted for another fifty years, Zwicky wrote that the galaxies must be held together by "''dunkle Materie''" (dark matter).<ref>{{cite journal |last1=Zwicky |first1=F. |title=Die Rotverschiebung von extragalaktischen Nebeln |journal=Helvetica Physica Acta |date=1933 |volume=6 |pages=110–127 |bibcode=1933AcHPh...6..110Z |url=https://articles.adsabs.harvard.edu//full/1933AcHPh...6..110Z/0000110.000.html |trans-title=The red shift of extragalactic neubulae |language=German}}  From p 125:  ''"Um, wie beobachtet, einen mittleren Dopplereffekt von 1000 km/sek oder mehr zu erhalten, müsste also die mittlere Dichte im Comasystem mindestens 400 mal grösser sein als die auf Grund von Beobachtungen an leuchtender Materie abgeleitete.  Falls sich dies bewahrheiten sollte, würde sich also das überraschende Resultat ergeben, dass dunkle Materie in sehr viel grösserer Dichte vorhanden ist als leuchtende Materie."'' (In order to obtain an average Doppler effect of 1000 km/s or more, as observed, the average density in the Coma system would thus have to be at least 400 times greater than that derived on the basis of observations of luminous matter. If this were to be verified, the surprising result would then follow that dark matter is present in very much greater density than luminous matter.)</ref><ref>{{cite journal | last1=de Swart| first1=J. G.| last2=Bertone| first2=G.| last3=van Dongen| first3=J.| title=How dark matter came to matter| journal=Nature Astronomy| date=2017| volume=1| issue=59| page=0059| doi=10.1038/s41550-017-0059| arxiv = 1703.00013 | bibcode = 2017NatAs...1E..59D |s2cid=119092226}}</ref>

About 90% of the mass of the Coma cluster is believed to be in the form of [[dark matter]].  The distribution of dark matter throughout the cluster, however, is poorly constrained{{clarify|date=April 2023}}.<ref>{{Cite journal | author = Merritt, D. | author-link = David Merritt | title = The Distribution of Dark Matter in the Coma Cluster | journal = The Astrophysical Journal | volume = 313 | pages = 121–135 |date=February 1987 | bibcode = 1987ApJ...313..121M | doi = 10.1086/164953| doi-access = free }}</ref>

==X-ray source==
An extended X-ray source centered at 1300+28 in the direction of the Coma cluster of galaxies was reported before August 1966.<ref name=Boldt>{{ cite journal
|vauthors=Boldt E, McDonald FB, Riegler G, Serlemitsos P | title = Extended source of energetic cosmic X rays
| date = 1966
| journal = Phys. Rev. Lett.
| volume = 17
| issue = 8
| pages = 447–50
| doi = 10.1103/PhysRevLett.17.447
| bibcode = 1966PhRvL..17..447B
}}</ref> This X-ray observation was performed by balloon, but the source was not detected in the [[sounding rocket]] flight launched by the X-ray astronomy group at the [[Naval Research Laboratory]] on November 25, 1964.<ref name=Friedman>{{ cite journal 
|vauthors=Friedman H, Byram ET | title = X-rays from the Coma cluster of galaxies
| journal = Astrophysical Journal
|date=January 1967
| volume = 147
| issue = 1
| pages = 399–401
| bibcode = 1967ApJ...147..368.
| doi = 10.1086/149022
| s2cid = 4286878
}}</ref> A strong X-ray source was observed by the X-ray observatory satellite [[Uhuru (satellite)|Uhuru]] close to the center of the Coma cluster and this source was suggested to be designated Coma X-1.<ref name=Gursky>{{ cite journal
|vauthors=Gursky H, Kellogg E, Murray S, Leong C, Tananbaum H, Giacconi R | title = A strong X-ray source in the Coma cluster observed by ''Uhuru''
| journal = Astrophysical Journal
|date=Aug 1971
| volume=167
| issue = 8
| pages = L81–4
| bibcode = 1971ApJ...167L..81G
| doi = 10.1086/180765
| doi-access = free
}}</ref>
The Coma cluster contains about 800 galaxies within a 100 x 100 arc-min area of the celestial sphere. The source near the center at [[Right ascension|RA]] (1950) 12<sup>h</sup>56<sup>m</sup> ± 2<sup>m</sup> [[Declination|Dec]] 28°6' ± 12' has a luminosity L<sub>x</sub> = 2.6 x 10<sup>44</sup> ergs/s.<ref name=Gursky/> As the source is extended, with a size of about 45', this argues against the possibility that a single galaxy is responsible for the emission.<ref name=Gursky/> The Uhuru observations indicated a source strength of no greater than ~10<sup>−3</sup> photons cm<sup>−2</sup>s<sup>−1</sup>keV<sup>−1</sup> at 25 keV,<ref name=Gursky/> which disagrees with the earlier observations<ref name=Boldt/> claiming a source strength of ~10<sup>−2</sup> photons cm<sup>−2</sup>s<sup>−1</sup>keV<sup>−1</sup> at 25 keV, and a size of 5°.{{clear}}

==Gallery==

<gallery>
File:Clusters within clusters - Coma Cluster.jpg|Thousands of globular clusters lying at the core of a galaxy cluster<ref>{{cite web |title=Clusters within clusters |url=https://www.spacetelescope.org/images/potw1849a/ |website=www.spacetelescope.org |access-date=3 December 2018}}</ref>
File:The Coma Galaxy Cluster as seen by Hubble Heic0813a.jpg|A large portion of the Coma Cluster seen by Hubble's Advanced Camera for Surveys
File:Hubble close-up on the Coma Cluster.jpg|Hubble close-up on the Coma Cluster<ref>{{cite news|title=Hubble close-up on the Coma Cluster|url=http://www.spacetelescope.org/images/potw1402a/|access-date=18 January 2014|newspaper=ESA/Hubble Picture of the Week}}</ref>
File:NGC 4911.jpg|A face-on view of a spiral galaxy ([[NGC 4911]]) located deep within the Coma Cluster
File:Coma Cluster of Galaxies (visible, wide field).jpg|Wide field image of the Coma Cluster taken at the Mount Lemmon SkyCenter using the 0.8m Schulman Telescope
File:ComaGalaxy.jpg|Coma Cluster photographed through 8" Celestron Edge HD in San Diego, CA.<ref>{{Cite web|url=http://www.astrobin.com/244071/|title = Coma Cluster}}</ref>
File:Coma cluster.png|Coma cluster by amateur astrophotographer Anthony MICHEL<ref>{{cite web|title=Coma cluster |url=https://app.astrobin.com/i/94s8qc}}<!-- auto-translated from French by Module:CS1 translator --></ref>
File:Comacl zentrum600.png|Map of the central part of the Coma Cluster.
</gallery>

==See also==
* [[List of Abell clusters]]
* [[List of galaxy groups and clusters]]
* [[Eridanus Cluster]]
* [[Fornax Cluster]] – ''another nearby cluster of galaxies''
* [[Norma Cluster]]
* [[Virgo Cluster]] – ''another nearby cluster of galaxies''
* [[X-1 X-ray source]]

==References==
{{reflist}}

==External links==
{{commons category}}
* [http://antwrp.gsfc.nasa.gov/apod/ap000806.html The Coma Cluster of Galaxies] – [[Astronomy Picture of the Day]], NASA, 2000 August 6
* [http://astrojan.nhely.hu/comacl.htm The clickable Coma galaxy cluster]
* [https://arxiv.org/abs/astro-ph/0212432 The dynamical state of the Coma cluster with XMM-Newton]
* [https://arxiv.org/abs/astro-ph/0405582 Very Small Array observations of the Sunyaev-Zel'dovich effect in nearby galaxy clusters]
* [http://astronomy.swin.edu.au/coma/index-mm.htm Hubble Space Telescope Treasury Survey of the Coma Cluster]
* {{WikiSky|name=The Coma Cluster|z=9}}

{{Sky|12|59|49|+|27|58|50|332700000}}
{{Catalogs|Abell=1656}}
{{Coma Berenices}}
{{Galaxy}}

{{DEFAULTSORT:Coma Cluster}}
[[Category:Coma Cluster| ]]
[[Category:Galaxy clusters]]
[[Category:Coma Supercluster]]
[[Category:Coma Berenices]]
[[Category:Abell objects|1656]]
[[Category:Abell richness class 2]]