View source for Omega Centauri

{{Short description|Globular cluster in the constellation Centaurus}}
{{About-distinguish|ω Centauri|HD 110458{{!}}w Centauri}}
{{Infobox globular cluster
| name = Omega Centauri
| image = [[Image:Omega Centauri Stars.png|300px]]
|caption= The globular cluster Omega Centauri
| epoch = [[Epoch (astronomy)#Julian years and J2000|J2000]]
| class = VIII<ref name=hcob849_11/>
| ra = {{RA|13|26|47.28}}<ref name=aj140_6_1830/>
| dec = {{DEC|−47|28|46.1}}<ref name=aj140_6_1830/>
| dist_ly = {{cvt|15.8|+/-|1.1|kly|kpc|lk=on}}<ref name="vandeVenetal2006"/><!-- note 2006 paper states dynamical bestfit is 4.8 ± 0.3 pc, canonical value from photometric methods is 5.0 ± 0.2; whereas hubblesite simplifies to 17000 ly -->
| appmag_v = 3.9<ref name="Skiff1999"/>
| size_v = 36′.3<ref name="ArnoldDohertyMoore1999"/>
| constellation = [[Centaurus]]
| mass_kg = 
| mass_msol = {{Val|4.05|0.1|e=6}}<ref name="MNRAS429_3_1887"/>
| radius_ly = 86 ± 6 ly<ref>distance × sin(diameter_angle / 2), using distance of 5 kpc and angle 36.3′<!-- where is this sourced? -->, = 86 ± 6 ly radius<!-- ±6 ly is from min to max distances from 2006 paper: 4.5 to 5.2kpc --></ref>
| v_hb = 
| metal_fe = –1.35<ref name=mnras404_3_1203/>
| age = 11.52&nbsp;[[Gigayear|Gyr]]<ref name=mnras404_3_1203/>
| notes = 
| names = [[New General Catalogue|NGC]]&nbsp;5139,<ref name="simbad"/> GCl&nbsp;24,<ref name="simbad"/> ω&nbsp;Centauri,<ref name="vandeVenetal2006"/> [[Caldwell catalogue|Caldwell]] 80, [[Melotte catalogue|Mel]] 118
}}
'''Omega Centauri''' (ω Cen, NGC 5139, or Caldwell 80) is a [[globular cluster]] in the [[constellation]] of [[Centaurus]] that was first identified as a non-stellar object by [[Edmond Halley]] in 1677. Located at a distance of {{convert|17090|ly|pc|abbr=off|lk=on}}, it is the largest known globular cluster in the [[Milky Way]] at a diameter of roughly 150 light-years.<ref>{{cite web|title=Omega Centauri: The Largest Globular Cluster|url=http://www.universeforfacts.com/2013/11/omega-centauri-largest-globular-cluster.html|archive-url=https://web.archive.org/web/20141221221834/http://www.universeforfacts.com/2013/11/omega-centauri-largest-globular-cluster.html|url-status=usurped|archive-date=December 21, 2014|website=Universe for Facts|access-date=21 December 2014}}</ref> It is estimated to contain approximately 10 million stars, with a total mass of 4 million [[solar mass]]es,<ref>{{Cite web | url=http://apod.nasa.gov/apod/ap100331.html | title=APOD: 2010 March 31 - Millions of Stars in Omega Centauri}}</ref> making it the most massive known globular cluster in the Milky Way.

Omega Centauri is very different from most other galactic globular clusters to the extent that it is thought to have originated as the core remnant of a disrupted [[dwarf galaxy]].<ref name=AJ676_2_1008/> There is evidence of an [[intermediate-mass black hole]] in the dense core of this cluster, although this is disputed.

==Observation history==
Around 150 AD, Greco-Roman writer and astronomer [[Ptolemy]] catalogued this object in his ''[[Almagest]]'' as a star on the centaur's back, "Quae est in principio scapulae". German cartographer [[Johann Bayer]] used Ptolemy's data to [[Bayer designation|designate]] this object "Omega Centauri" with his 1603 publication of ''[[Uranometria]]''.<ref>{{cite book |last1=Bayer |first1=Johann |title=Uranometria |date=1603 |publisher=Christoph Mang |location=Augsburg, [Germany] |language=la}} Available at: [http://lhldigital.lindahall.org/cdm/ref/collection/astro_atlas/id/118 Linda Hall Library (University of Missouri (Kansas City, Missouri, US))] {{Webarchive|url=https://web.archive.org/web/20180724203818/http://lhldigital.lindahall.org/cdm/ref/collection/astro_atlas/id/118 |date=2018-07-24 }} The pages of this book are not numbered. However, towards the end of the book there appears ''"Tabula quadragesima prima, Centaurus."'' (Forty-first table, Centaur). The table lists Omega Centauri as ''"21 ω In imo dorso"'' (21 ω At the bottom of the back). The following page shows the constellation Centaur and Omega Centauri as a star labelled ω at the base of the Centaur's back.</ref> Using a telescope from the South Atlantic island of [[Saint Helena]], English astronomer [[Edmond Halley]] observed this object in 1677, listing it as a non-stellar object. In 1716, it was published by Halley among his list of six "luminous spots or patches" in the ''[[Philosophical Transactions of the Royal Society]]''.<ref>See:
* {{cite journal |last=Halley |first=Edmond |title=An account of several nebualæ or lucid spots like clouds, lately discovered among the fixt stars by help of the telescope |journal=Philosophical Transactions of the Royal Society of London |date=1716 |volume=29 |issue=347 |pages=390–392 |url=https://babel.hathitrust.org/cgi/pt?id=mdp.39076000296926;view=1up;seq=427|doi=10.1098/rstl.1714.0046 |s2cid=186215009 |doi-access= |url-access=subscription }} ; see p. 391. 
* Reprinted at: [http://www.messier.seds.org/xtra/similar/halley_pt.html SEDS: The Messier Catalog]</ref><ref name="OMeara2013"/>

Swiss astronomer [[Jean-Philippe de Cheseaux]] included Omega Centauri in his 1746 list of 21 [[nebula]]e,<ref name="OMeara2013"/><ref>Cheseaux compiled a list of nebulae during 1745–1746. He sent the list to his grandfather, in the form of a letter. The letter was read before the French Academy of Sciences in 1746. However, it was first published only in 1892 as part of a large article by the French astronomer [[Guillaume Bigourdan]]. 
* {{cite journal |last1=Bigourdan |first1=G. |title=Observations de nébuleuses et d'amas stellaires |journal=Annales de l'Observatoire de Paris. Observations. 1884. |date=1892 |pages=G-1 – G-103 |url=https://babel.hathitrust.org/cgi/pt?id=osu.32435055017743&view=1up&seq=657 |trans-title=Observations of nebulae and of stellar clusters |language=fr}} Cheseaux's letter (in French) appears on pp. G-8 – G-9.
* An English translation of Cheseaux's letter appears in: {{cite journal |last1=Jones |first1=Kenneth Glyn |title=The search for the nebulae - V. |journal=Journal of the British Astronomical Association |date=1969 |volume=79 |pages=105–112|bibcode=1969JBAA...79..105J }} An English translation of Cheseaux's letter appears on pp. 105–106. Available at: [http://articles.adsabs.harvard.edu//full/1969JBAA...79..105J/0000105.000.html SAO/NASA Astrophysics Data System]
* See also: [http://www.messier.seds.org/xtra/Bios/decheseaux.html#bigourdan1892 Philippe Loys de Chéseaux (May 4, 1718 – November 30, 1751) at SEDS: The Messier Catalog]</ref> as did French astronomer [[Lacaille]] in 1755, whence the catalogue number is designated L I.5.<ref>{{cite journal |last1=de la Caille |title=Sur les étoiles nébuleuses du ciel austral |journal=Histoire de l'Académie Royale des Sciences, avec les Mémoires de Mathématique & de Physique |date=1755 |volume=1755 |pages=194–199 |url=https://www.biodiversitylibrary.org/item/88652#page/394/mode/1up |trans-title=On the nebulous stars of the southern sky |language=fr}} ; see in the table on p. 196: ''"Nébuleuse du Centaure ... "'' Note: The catalog number "L I.5" designates: that the nebula is listed in Lacaille's catalog of 1755 (hence the "L"); that Omega Centauri is a nebula of the "first type" (''première espèce'', namely, nebulae that do not seem to be accompanied by stars when viewed via a telescope that is 2 feet long; hence the Roman numeral "I"); and that Omega Centauri is listed fifth among the nebulae of the first type (hence the "5"). See: [http://www.docdb.net/show_object.php?id=ngc_5139 Deep Sky Observer's Companion – the online database]</ref> It was first recognized as a globular cluster by Scottish astronomer [[James Dunlop]] in 1826, who described it as a "beautiful globe of stars very gradually and moderately compressed to the centre".<ref name="PTRS118_615"/><ref name="Harrington2013"/>

In 2025, observations from the James Webb Space Telescope (JWST) and the Hubble Space Telescope (HST) revealed new details about the stellar populations and internal dynamics of Omega Centauri, particularly in the outer regions (0.9–2.3 half-light radii). Using chromosome maps (ChMs), astronomers identified two major population groups: a Lower Stream (LS), composed of first-generation stars with low helium and nitrogen, and an Upper Stream (US), containing stars enriched in helium and nitrogen but depleted in oxygen. These populations also differ kinematically, with US stars exhibiting more radially anisotropic orbits and LS stars showing higher tangential velocity dispersion and stronger rotation. Within the US, chemically "intermediate" and "extreme" subpopulations showed a gradient in orbital anisotropy. While metallicity had only a modest effect on stellar motions, the overall low level of energy equipartition and its radial variation suggest that Omega Centauri is not fully dynamically relaxed. These findings reinforce the idea that Omega Centauri is the remnant core of a disrupted dwarf galaxy rather than a typical globular cluster.<ref>{{cite web|url=https://arxiv.org/pdf/2506.21187v1|title=A Joint JWST and HST View of Omega Centauri: Multiple Stellar Populations and Their Kinematics|access-date=2025-06-27}}</ref>

==Properties==
At a distance of about {{convert|17000|ly|pc|abbr=off}} from [[Earth]], Omega Centauri is one of the few globular clusters visible to the naked eye—and appears almost as large as the full [[Moon]] when seen from a dark, rural area.<ref name=ESA/> It is the brightest, largest and, at 4 million [[solar mass]]es,<ref name="MNRAS429_3_1887"/> the most massive-known globular cluster associated with the Milky Way. Of all the globular clusters in the [[Local Group]] of galaxies, only [[Mayall II]] in the [[Andromeda Galaxy]] is brighter and more massive.<ref name="FrommertKronberg1998"/> Orbiting through the Milky Way, Omega Centauri contains several million [[Population II]] stars and is about 12 billion years old.<ref name="hubblesite"/>

The stars in the core of Omega Centauri are so crowded that they are estimated to average only 0.1 light-year away from each other.<ref name="hubblesite"/> The internal dynamics have been analyzed using measurements of the [[radial velocities]] of 469 stars.<ref name=ApJ114_1074/> The members of this cluster are orbiting the [[center of mass]] with a peak [[velocity dispersion]] of 7.9&nbsp;km s<sup>−1</sup>. The mass distribution inferred from the kinematics is slightly more extended than, though not strongly inconsistent with, the luminosity distribution.{{cn|date=October 2020}}

===Members===
These stars are the well studied members of the cluster. Some are abundant in metals and  elements. (eg. Iron, Carbon, Oxygen)<ref>{{Cite journal |last=Johnson |first=Christian I. |last2=Pilachowski |first2=Catherine A. |date=October 2010 |title=Chemical Abundances for 855 Giants in the Globular Cluster Omega Centauri (NGC 5139) |url=https://ui.adsabs.harvard.edu/abs/2010ApJ...722.1373J/abstract |journal=The Astrophysical Journal |language=en |volume=722 |issue=2 |pages=1373–1410 |doi=10.1088/0004-637X/722/2/1373 |issn=0004-637X}}</ref><ref>{{Cite journal |last=Jofré |first=P. |last2=Aguilera-Gómez |first2=C. |last3=Villarreal |first3=P. |last4=Cubillos |first4=F. A. |last5=Das |first5=P. |last6=Hua |first6=X. |last7=Yates |first7=R. |last8=Silva |first8=P. |last9=Vitali |first9=S. |last10=Peña |first10=T. |last11=Signor |first11=T. |last12=Walsen |first12=K. |last13=Tissera |first13=P. |last14=Rojas-Arriagada |first14=A. |last15=Johnston |first15=E. |date=July 2025 |title=Studying stellar populations in Omega Centauri with phylogenetics |url=https://ui.adsabs.harvard.edu/abs/2025A&A...699A.291J/abstract |journal=Astronomy and Astrophysics |language=en |volume=699 |pages=A291 |doi=10.1051/0004-6361/202554863 |issn=0004-6361}}</ref>
{| class="wikitable sortable “wikitable”"
! [[Proper names (astronomy)|Star Name]]
! [[Stellar classification|Spectral<br />type]]
!Star Type
|-
|Central Black Hole
| BH(IMBH)
|Intermediate Mass Black Hole
|-
|Variable Star 2
| {{StarM|M III}}
|Red Giant
M type AGB Variable (Semi Regular)
|-
|Variable Star 6
| {{StarM|M III}}
|Red Giant
M type AGB Variable (Semi Regular)
|-
|Variable Star 42
| {{StarM|M III}}
|Red Giant
M type AGB Variable (Semi Regular)
|-
|Variable Star 147
| {{StarM|M III}}
|Red Giant
M type AGB Variable (Semi Regular)
|-
|ROA 102
| {{StarM|M III}}
|Red Giant
M type RGB
|-
|Omega Centauri 65
| {{StarK|K III}}
|Orange Giant
K type RGB
|-
|Omega Centauri 74
| {{StarK|K III}}
|Orange Giant
K type RGB
|-
|Omega Centauri 91
| {{StarK|K III}}
|Orange Giant
K type RGB
|-
|Omega Centauri 101
| {{StarK|K III}}
|Orange Giant
K type RGB
|-
|Star #124
| {{StarK|K III}}
|Orange Giant
K type RGB
|-
|ROA 24
| {{StarK|K III}}
|Orange Giant
K type RGB
|-
|ROA 46
| {{StarK|K III}}
|Orange Giant
K type RGB
|-
|ROA 65
| {{StarK|K III}}
|Orange Giant
K type RGB
|-
|ROA 74
| {{StarK|K III}}
|Orange Giant
K type RGB
|-
|ROA 91
| {{StarK|K III}}
|Orange Giant
K type RGB
|-
|ROA 101
| {{StarK|K III}}
|Orange Giant
K type RGB
|-
|ROA 123
| {{StarK|K III}}
|Orange Giant
K type RGB
|-
|ROA 139
| {{StarK|K III}}
|Orange Giant
K type RGB
|-
|ROA 256
| {{StarK|K III}}
|Orange Giant
K type RGB
|-
|ROA 270
| {{StarK|K III}}
|Orange Giant
K type RGB
|-
|ROA 276
| {{StarK|K III}}
|Orange Giant
K type RGB
|-
|ROA 577
| {{StarK|K III}}
|Orange Giant
K type RGB
|-
|(An unnamed star)
| {{StarK|K III}}
|Orange Giant
K type RGB Red Straggler CH Star
|-
|Variable Star 1
| {{StarG|G III}}
|Yellow Giant
Variable (RR Lyrae type)
|-
|Variable Star 15
| {{StarG|G III}}
|Yellow Giant
|-
|ROA 279
| {{StarG|G III}}
|Yellow Giant
|-
|}

===Common stars in the cluster===
These are the common or notable types of stars in the cluster. For the binary stars, the spectral class here is the primary stars’ sprctral class.

{| class="wikitable sortable “wikitable”"
! [[Proper names (astronomy)|Star Name]]
! [[Stellar classification|Spectral<br />type]]
|-
|Red Giants
(M type RGB)
| {{StarM|M III}}
|-
|Red Giants
(M type AGB)
| {{StarM|M III}}
|-
|Orange Giants
(K type RGB)
| {{StarK|K III}}
|-
| rowspan="2" |Yellow Giants
| {{StarG|G III}}
|-
| {{StarF|F III}}
|-
|Blue Giants
| {{StarB|B III}}
|-
| rowspan="5" |Main Sequence Stars
| {{StarB|B V}}
|-
| {{StarA|A V}}
|-
| {{StarF|F V}}
|-
| {{StarG|G V}}
|-
| {{StarK|K V}}
|-
| rowspan="2" |Semi-Regular Variables
| {{StarM|M III}}
|-
| {{StarK|K III}}
|-
| rowspan="2" |Irregular Variables
| {{StarM|M III}}
|-
| {{StarK|K III}}
|-
|Carbon Stars
| {{StarM|M(CR/CN) III}}
|-
|Zirconium(S type) Stars
| {{StarM|M(S) III}}
|-
|CH Stars
| {{StarK|K III}}
|-
|Red Stragglers
| {{StarK|K III}}
|-
|Symbiotic binaries
| {{StarK|K III}}
|-
| rowspan="2" |Population II Cepheids
| {{StarK|K III}}
|-
| {{StarG|G III}}
|-
| rowspan="3" |Eclisping Binaries
| {{StarM|M III}}
|-
| {{StarK|K III/IV/V}}
|-
| {{StarG|G III/IV/V}}
|-
| rowspan="2" |Subgiants
| {{StarK|K IV}}
|-
| {{StarG|G IV}}
|-
| rowspan="3" |RR Lyrae Variables
| {{StarG|G III}}
|-
| {{StarF|F III}}
|-
| {{StarA|A III}}
|-
| rowspan="2" |Blue Stragglers
| {{StarA|A V}}
|-
| {{StarB|B V}}
|-
| rowspan="2" |SX Phoenicis Variables
| {{StarA|A V}}
|-
| {{StarF|F V}}
|-
| rowspan="3" |BY Draconis Variables
| {{StarG|G V}}
|-
| {{StarK|K V}}
|-
| {{StarM|M V}}
|-
| rowspan="2" |Cataclysmic Variables
| {{StarK|K V}}
|-
| {{StarM|M V}}
|-
|Red dwarfs
| {{StarM|M V}}
|-
|Blue Subdwarfs
| {{StarB|B VI(sdB)}}
|-
|Stellar remnants
(White Dwarfs,Neutron Stars,
Stellar Black Holes)
|D/WD/VII
NS
BH(SBH)
|}

===Evidence of a central black hole===
[[File:Central Region Omega Centauri.jpg|thumb|right|200px|{{center|The central region of Omega Centauri. The lower illustration charts the future positions of the stars highlighted by the white box in the top image. Each streak represents the star's predicted motion over the next 600 years. The period between dots corresponds to 30 years. October 2010}}]]
A 2008 study presented evidence for an [[intermediate-mass black hole]] at the center of Omega Centauri, based on observations made by the [[Hubble Space Telescope]] and [[Gemini Observatory]] on [[Cerro Pachón]] in Chile.<ref name="Noyola2008"/><ref name="ESA2008"/> Hubble's [[Advanced Camera for Surveys]] showed that stars are bunching up near the center of Omega Centauri, as evidenced by the gradual increase in starlight near the center. Using instruments at the Gemini Observatory to measure the speed of stars swirling in the cluster's core, E. Noyola and colleagues found that stars closer to the core are moving faster than stars farther away. This measurement was interpreted to mean that unseen matter at the core is interacting gravitationally with nearby stars. By comparing these results with standard models, the astronomers concluded that the most likely cause was the gravitational pull of a dense, massive object such as a black hole. They calculated the object's mass at 40,000 [[solar mass]]es.<ref name="Noyola2008"/>

More recent work has challenged conclusions that there is a black hole in the cluster's core, in particular disputing the proposed location of the cluster center.<ref name="anderson2010"/><ref name="vanderMarel2010"/> Calculations using a revised location for the center found that the velocity of core stars does not vary with distance, as would be expected if an intermediate-mass black hole were present. The same studies also found that starlight does not increase toward the center but instead remains relatively constant. The authors noted that their results do not entirely rule out the black hole proposed by Noyola and colleagues, but they do not confirm it, and they limit its maximum mass to 12,000 solar masses.

A study from July 10, 2024 has examined seven fast-moving stars from the center of Omega Centauri and found that their speeds were consistent with an intermediate-mass black hole of at least 8,200 solar masses.<ref>{{Cite journal |title=Fast-moving stars around an intermediate-mass black hole in Omega Centauri |journal=Nature |last1=Haberle |first1=Maximiliam |last2=and 17 others |date=10 July 2024|volume=631 |issue=8020 |pages=285–288 |doi=10.1038/s41586-024-07511-z |pmid=38987499 |pmc=11236702 |arxiv=2405.06015 |bibcode=2024Natur.631..285H }}</ref>

=== Disrupted dwarf galaxy===
[[File:Omega Centauri by ESO.jpg|thumb|left|Captured with the WFI camera from ESO's La Silla Observatory]]
It has been speculated that Omega Centauri is the core of a [[dwarf galaxy]] that was disrupted and absorbed by the Milky Way.<ref name="HubbleSite"/> Indeed, [[Kapteyn's Star]], which is currently only 13 light-years away from Earth, is thought to originate from Omega Centauri.<ref name="AAA550_A26"/> Omega Centauri's chemistry and motion in the Milky Way are also consistent with this picture.<ref name=ESA/> Like Mayall II, Omega Centauri has a range of [[Metallicity|metallicities]] and stellar ages that suggests that it did not all form at once (as globular clusters are thought to form) and may in fact be the remainder of the core of a smaller galaxy long since incorporated into the Milky Way.<ref name="BAAS30_1348"/>

==In fiction==
The novel ''Singularity'' (2012), by [[William H. Keith Jr.|Ian Douglas]], presents as fact that Omega Centauri and [[Kapteyn's Star]] originate from a disrupted dwarf galaxy, and this origin is central to the novel's plot. A number of scientific aspects of Omega Centauri are discussed as the story progresses, including the likely radiation environment inside the cluster and what the sky might look like from inside the cluster.<ref name="Douglas2012"/>

The character Atlan has adventures in Omega Centauri in cycle 7 of the ''Atlan'' series, a spinoff of the German science fiction series ''Perry Rhodan.''<ref>{{cite web | url=https://www.perrypedia.de/wiki/Centauri_(Zyklus) | title=Centauri (Zyklus) – Perrypedia }}</ref>

==See also==
* [[Canis Major Overdensity]]
* [[Fimbulthul stream]]
* [[Mayall II]]
* [[Messier 54]]
* [[NGC 5286]]
* [[Sagittarius Dwarf Spheroidal Galaxy]]
* [[List of largest known star clusters]]

{{clear}}

==References==
{{reflist|30em|refs=
<ref name="Skiff1999">{{Citation
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 |title        = Observational Data for Galactic Globular Clusters
 |work         = The NGC/IC Project
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}}</ref>

<ref name="OMeara2013">{{Citation
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<ref name="ArnoldDohertyMoore1999">{{Citation
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<ref name="ESA2008">{{Citation
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<ref name="Harrington2013">{{Citation
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<ref name=ApJ114_1074>{{cite journal
 | last1 = Merritt
 | first1 = David
 | author-link = David Merritt
 | last2 = Meylan
 | first2 = Georges
 | last3 = Mayor
 | first3 = Michel
 | author3-link = Michel Mayor
 | title = The stellar dynamics of Omega Centauri
 | journal = The Astrophysical Journal
 |date=September 1997
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<ref name="PTRS118_615">{{cite journal
 | last1   = Dunlop
 | first1  = J.
 | title   = A catalogue of nebulae and clusters of stars in the southern hemisphere, observed at Parramatta in New South Wales
 | journal = Philosophical Transactions of the Royal Society
 | bibcode = 1828RSPT..118..113D
 | date    = 1828
 | volume  = 118
 | pages   = 113–151
 | doi=10.1098/rstl.1828.0010
 | url     = https://babel.hathitrust.org/cgi/pt?id=hvd.hxkbyy&view=1up&seq=133
| doi-access= free
 | url-access= subscription
 }} Omega Centauri is listed as No. 440 on p. 136.</ref>

<ref name="Noyola2008">{{cite journal
 | last1 = Noyola | first1= E.
 | last2= Gebhardt | first2= K. 
 | last3 = Bergmann | first3 = M.
 | title = Gemini and Hubble Space Telescope Evidence for an Intermediate-Mass Black Hole in ω Centauri
 | journal = The Astrophysical Journal
 | arxiv = 0801.2782
 |date=April 2008
 | volume = 676
 | issue = 2
 | pages = 1008–1015
 | doi = 10.1086/529002
 | bibcode = 2008ApJ...676.1008N
| s2cid= 208867075
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<ref name=ESA>{{Cite news | title = Black hole found in Omega Centauri| publisher = ESA| date = 2008-04-02| url = http://www.esa.int/esaSC/SEMPGM5QGEF_index_0.html| access-date = 2009-11-06}}</ref>

<ref name=AJ676_2_1008>{{cite journal | first1=Eva | last1=Noyola | first2=Karl | last2=Gebhardt | first3=Marcel | last3=Bergmann | title=Gemini and Hubble Space Telescope Evidence for an Intermediate Mass Black Hole in omega Centauri | doi=10.1086/529002 | date=2008 | journal=The Astrophysical Journal | volume=676 | issue=2 | pages=1008 | arxiv=0801.2782 | bibcode=2008ApJ...676.1008N | s2cid=208867075 }}</ref>

<ref name="HubbleSite">{{Cite press release| title = Astronomers Find Suspected Medium-Size Black Hole in Omega Centauri| date = 2008-04-02| url = http://hubblesite.org/newscenter/archive/releases/2008/14/full/| access-date = 2009-11-06}}</ref>

<ref name="anderson2010">{{cite journal
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<ref name="vanderMarel2010">{{cite journal
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<ref name="MNRAS429_3_1887">{{citation
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<ref name="FrommertKronberg1998">{{Citation
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<ref name="AAA550_A26">{{citation
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<ref name=aj140_6_1830>{{citation | display-authors=1 | last1=Goldsbury | first1=Ryan | last2=Richer | first2=Harvey B. | last3=Anderson | first3=Jay | last4=Dotter | first4=Aaron | last5=Sarajedini | first5=Ata | last6=Woodley | first6=Kristin | title=The ACS Survey of Galactic Globular Clusters. X. New Determinations of Centers for 65 Clusters | journal=The Astronomical Journal | volume=140 | issue=6 | pages=1830–1837 |date=December 2010 | doi=10.1088/0004-6256/140/6/1830 | bibcode=2010AJ....140.1830G | postscript=. |arxiv = 1008.2755 | s2cid=119183070 }}</ref>

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<ref name=mnras404_3_1203>{{citation | last1=Forbes | first1=Duncan A. | last2=Bridges | first2=Terry | title=Accreted versus in situ Milky Way globular clusters | journal=Monthly Notices of the Royal Astronomical Society | volume=404 | issue=3 | pages=1203–1214 |date=May 2010 | doi=10.1111/j.1365-2966.2010.16373.x | doi-access=free | bibcode=2010MNRAS.404.1203F | postscript=. |arxiv = 1001.4289 | s2cid=51825384 }}</ref>

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<ref name="simbad">{{cite simbad | title=NGC 5139 | access-date=2006-11-16 }}</ref>

<ref name="vandeVenetal2006">{{cite journal | last1=van de Ven | first1=G. | last2=van den Bosch | first2=R. C. E. | last3=Verolme | first3=E. K. | last4=de Zeeuw | first4=P. T. | title=The dynamical distance and intrinsic structure of the globular cluster ω Centauri | journal=Astronomy and Astrophysics | date=2 January 2006 | volume=445 | issue=2 | pages=513–543 | bibcode=2006A&A...445..513V | doi=10.1051/0004-6361:20053061 | quote=best-fit dynamical distance D=4.8±0.3 kpc ... consistent with the canonical value 5.0±0.2 kpc obtained by photometric methods|arxiv = astro-ph/0509228 | s2cid=15538249 }}</ref><!-- 15.8 ±1.1 kly is from min to max distances from 2006 paper: 4.5 to 5.2kpc -->

<ref name="Douglas2012">{{cite book |last=Douglas |first=Ian |title=Singularity |date=2012 |publisher=Harper Voyager |isbn=978-0061840272}}</ref>


}}

==Further reading==
* {{cite journal |title= The Shards of ω Centauri |author1=Myeong, G. C. |author2=Evans, N. W. |author3=Belokurov, V. |author4=Sanders, J. L. |author5=Koposov, S. E. |date= April 2018 |arxiv= 1804.07050 |bibcode= 2018arXiv180407050M |journal= Monthly Notices of the Royal Astronomical Society | doi = 10.1093/mnras/sty1403 |doi-access=free }}

==External links==
{{Commons category|NGC 5139|Omega Centauri}}

* [http://hubblesite.org/newscenter/newsdesk/archive/releases/2001/33/image/a Hubblesite - Peering into the core of a globular cluster]
* [http://www.constellation-guide.com/omega-centauri-ngc-5139/ Omega Centauri at Constellation Guide]
* [http://www.spacetelescope.org/images/html/opo0133a.html Omega Centauri at ESA/Hubble - link not operational] {{Webarchive|url=https://web.archive.org/web/20051227102031/http://www.spacetelescope.org/images/html/opo0133a.html |date=2005-12-27 }}
* [https://web.archive.org/web/20050615115719/http://control.com.au/bi2003/bi2410.shtml Omega Centauri: Former Core of a Dwarf Galaxy?]
* [http://gclusters.altervista.org/cluster_4.php?ggc=Omega+Cen Omega Centauri, Galactic Globular Clusters Database page]
* {{WikiSky}}
* [http://www.wikisky.org/?ra=13.44057&de=-47.482835&zoom=9&img_source=IMG_1403:all Omega Centauri on WikiSky - zoomed view]
* [http://msowww.anu.edu.au/news/media_releases/media_release_030716.php Omega Centauri: Proud Cluster or Sad Remnant?] {{Webarchive|url=https://web.archive.org/web/20060507223623/http://msowww.anu.edu.au/news/media_releases/media_release_030716.php |date=2006-05-07 }}
* [http://messier.seds.org/xtra/ngc/n5139.html SEDS] – NGC 5139
* [http://blackholes.stardate.org/objects/factsheet-omega-centauri.html StarDate: Omega Centauri Fact Sheet]

{{Sky|13|26|45.89|-|47|28|36.7|1000000000}}
{{Catalogs|NGC=5139|C=80}}
{{Caldwell catalogue}}
{{Stars of Centaurus}}
{{Ngc55}}
{{Portal bar|Astronomy|Stars|Outer space}}
{{DEFAULTSORT:Omega Centauri}}
[[Category:Astronomical objects known since antiquity]]
[[Category:Bayer objects|Centauri, Omega]]
[[Category:Caldwell objects|080b]]
[[Category:Centaurus]]
[[Category:Globular clusters]]
[[Category:Intermediate-mass black holes]]
[[Category:NGC objects]]