Westerlund 1: Difference between revisions
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{{Short description|Super star cluster in the Milky Way Galaxy}} |
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{{about|the super star cluster|the red supergiant star|Westerlund 1 W26}} |
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{{Infobox open cluster| |
{{Infobox open cluster| |
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| name = Westerlund 1 |
| name = Westerlund 1 |
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| ra = {{RA|16|47|04.0}}<ref name="brandner"/> |
| ra = {{RA|16|47|04.0}}<ref name="brandner"/> |
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| dec = {{DEC|−45|51|04.9}}<ref name="brandner"/> |
| dec = {{DEC|−45|51|04.9}}<ref name="brandner"/> |
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| dist_ly = {{val|3.78|0.56|0.46}}<ref name=gemma>{{cite |
| dist_ly = {{val|3.78|0.56|0.46}}<ref name=gemma>{{cite journal|arxiv=2005.02533|doi=10.1093/mnras/staa1290|title=Unlocking Galactic Wolf–Rayet stars with Gaia DR2 – II. Cluster and association membership|year=2020|last1=Parker|first1=Richard J.|last2=Crowther|first2=Paul A.|last3=Rate|first3=Gemma|journal=Monthly Notices of the Royal Astronomical Society|volume=495|pages=1209–1226|doi-access=free |s2cid=218516882}}</ref> (2.6<ref>{{Cite journal|last1=Aghakhanloo|first1=Mojgan|last2=Murphy|first2=Jeremiah W.|last3=Smith|first3=Nathan|last4=Parejko|first4=John|last5=Díaz-Rodríguez|first5=Mariangelly|last6=Drout|first6=Maria R.|last7=Groh|first7=Jose H.|last8=Guzman|first8=Joseph|last9=Stassun|first9=Keivan G.|date=2020-02-21|title=Inferring the parallax of Westerlund 1 from Gaia DR2|arxiv=1901.06582|bibcode=2020MNRAS.492.2497A|journal=Monthly Notices of the Royal Astronomical Society|volume=492|issue=2|pages=2497–2509|doi=10.1093/mnras/stz3628|doi-access=free |s2cid=119465620|issn=0035-8711}}</ref> – 4.23<ref name=Negueruela/>) [[parsec|kpc]] |
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| appmag_v = |
| appmag_v = |
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| size_v = |
| size_v = |
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| mass_kg = |
| mass_kg = |
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| mass_msol = 63,000<ref name=zwart>{{cite journal|doi=10.1146/annurev-astro-081309-130834|title=Young Massive Star Clusters|journal=Annual Review of Astronomy and Astrophysics|volume=48|pages=431–493|year=2010|last1=Portegies Zwart|first1=Simon F.|last2=McMillan|first2=Stephen L.W.|last3=Gieles|first3=Mark|bibcode=2010ARA&A..48..431P|arxiv = 1002.1961 |s2cid=119207843}}</ref> |
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| mass_msol = 63,000<ref name=zwart/> |
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| radius_ly = 3.26 ly<ref name=zwart/> |
| radius_ly = 3.26 ly<ref name=zwart/> |
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| v_hb = |
| v_hb = |
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| age = 3.50 Myr<ref name=zwart/> |
| age = 3.50 Myr<ref name=zwart/> |
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| constellation = [[Ara (constellation)|Ara]] |
| constellation = [[Ara (constellation)|Ara]] |
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| notes = |
| notes = |
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| names = Ara Cluster, [[Bengt Westerlund|Westerlund]] 1, [[ESO]] 277-12, C 1644-457, [[VDBH]] 197 |
| names = Ara Cluster, [[Bengt Westerlund|Westerlund]] 1, [[ESO]] 277-12, C 1644-457, [[VDBH]] 197 |
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| Simbad =ARA+CLUSTER |
| Simbad =ARA+CLUSTER |
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'''Westerlund 1''' (abbreviated '''Wd1''', sometimes called '''Ara Cluster'''<ref>{{cite journal|bibcode=1968ApJ...154L..67W|title=On the Extended Infrared Source in ARA|journal=Astrophysical Journal|volume=154|pages=L67|last1=Westerlund|first1=B. E.|year=1968|doi=10.1086/180270}}</ref>) is a compact young [[super star cluster]] |
'''Westerlund 1''' (abbreviated '''Wd1''', sometimes called '''Ara Cluster'''<ref>{{cite journal|bibcode=1968ApJ...154L..67W|title=On the Extended Infrared Source in ARA|journal=Astrophysical Journal|volume=154|pages=L67|last1=Westerlund|first1=B. E.|year=1968|doi=10.1086/180270|doi-access=free}}</ref>) is a compact young [[super star cluster]] about 3.8 [[kiloparsec|kpc]] (12,000 ly) away from Earth. It is thought to be the most massive young star cluster in the [[Milky Way]],<ref name=Negueruela>{{cite journal|doi=10.1051/0004-6361/202142985|title=Westerlund 1 under the light of Gaia EDR3: Distance, isolation, extent, and a hidden population |year=2022 |last1=Negueruela |first1=I. |last2=Alfaro |first2=E. J. |last3=Dorda |first3=R. |last4=Marco |first4=A. |last5=Maíz Apellániz |first5=J. |last6=González-Fernández |first6=C. |journal=Astronomy & Astrophysics |volume=664 |pages=A146 |arxiv=2204.00422 |bibcode=2022A&A...664A.146N |s2cid=247922758 }}</ref> and was discovered by [[Bengt Westerlund]] in 1961<ref>{{Cite journal |last=Westerlund |first=B. |date=1961 |title=A Heavily Reddened Cluster in Ara |journal=Astronomical Journal |volume=70 |page=57 |doi=10.1086/108585 |bibcode=1961AJ.....66T..57W|doi-access=free }}</ref> but remained largely unstudied for many years due to high [[interstellar extinction|interstellar absorption]] in its direction. In the future, it will probably evolve into a [[globular cluster]].<ref name=gallagher02>{{cite journal |
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| author = Gallagher |
| author = Gallagher |
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| author2 = Grebel |
| author2 = Grebel |
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| name-list-style = amp |
| name-list-style = amp |
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| date = 2002 |
| date = 2002 |
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| title = Extragalactic Star Clusters: Speculations on the Future |
| title = Extragalactic Star Clusters: Speculations on the Future |
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|arxiv = astro-ph/0109052 }}</ref> |
|arxiv = astro-ph/0109052 }}</ref> |
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The cluster contains a large number of rare, evolved, high-mass stars, including: 6 [[yellow hypergiant]]s, 4 [[red supergiant]]s including [[Westerlund 1-26]], one of the [[List of largest known stars|largest known stars]], 24 [[Wolf-Rayet stars]], a [[luminous blue variable]], many [[OB star|OB supergiants]], and an unusual supergiant [[B(e) star|sgB[e] star]] which has been proposed to be the remnant of a recent [[Stellar collision|stellar merger]].<ref name=clark>{{Cite journal | |
The cluster contains a large number of rare, evolved, high-mass stars, including: 6 [[yellow hypergiant]]s, 4 [[red supergiant]]s including [[Westerlund 1-26]], one of the [[List of largest known stars|largest known stars]], 24 [[Wolf-Rayet stars]], a [[luminous blue variable]], many [[OB star|OB supergiants]], and an unusual supergiant [[B(e) star|sgB[e] star]] which has been proposed to be the remnant of a recent [[Stellar collision|stellar merger]].<ref name=clark>{{Cite journal |last1=Clark |first1=J. S. |display-authors=etal |date=2005 |title=On the massive stellar population of the super star cluster Westerlund 1 |journal=Astronomy & Astrophysics |volume=434 |issue=3 |pages=949–969 |doi=10.1051/0004-6361:20042413 |bibcode=2005A&A...434..949C|arxiv = astro-ph/0504342 |last2=Negueruela |first2=I. |last3=Crowther |first3=P. A. |last4=Goodwin |first4=S. P. |s2cid=119042919 }}</ref> In addition, [[X-ray]] observations have revealed the presence of the [[anomalous X-ray pulsar]] [[CXOU J164710.2-455216|CXO J164710.20-455217]], a slow rotating [[neutron star]] that must have formed from a high-mass progenitor star.<ref>{{Cite journal |last1=Muno |first1=Michael P. |display-authors=etal |date=2006 |title=A Neutron Star with a Massive Progenitor in Westerlund 1 |journal=Astrophysical Journal Letters |volume=636 |issue=1 |pages=L41 |doi=10.1086/499776 |arxiv=astro-ph/0509408 |bibcode=2006ApJ...636L..41M|last2=Clark |first2=J. Simon |last3=Crowther |first3=Paul A. |last4=Dougherty |first4=Sean M. |last5=De Grijs |first5=Richard |last6=Law |first6=Casey |last7=McMillan |first7=Stephen L. W. |last8=Morris |first8=Mark R. |last9=Negueruela |first9=Ignacio |last10=Pooley |first10=David |last11=Portegies Zwart |first11=Simon |last12=Yusef-Zadeh |first12=Farhad |s2cid=10349450 }}</ref> Westerlund 1 is believed to have formed in a single burst of star formation, implying the constituent stars have similar ages and compositions. |
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Aside from hosting some of the most massive and least-understood stars in our galaxy, Westerlund 1 is useful as a relatively nearby, easy to observe [[super star cluster]] that can help astronomers determine what occurs within extragalactic super star clusters. |
Aside from hosting some of the most massive and least-understood stars in our galaxy, Westerlund 1 is useful as a relatively nearby, easy to observe [[super star cluster]] that can help astronomers determine what occurs within extragalactic super star clusters. |
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[[Image:Westerlund1 optical xray.jpg|thumb|left|upright=1.4|Images of Westerlund 1: left is visible light, with all stars appearing red due to interstellar absorption; right is X-ray wavelengths, with the magnetar marked]] |
[[Image:Westerlund1 optical xray.jpg|thumb|left|upright=1.4|Images of Westerlund 1: left is visible light, with all stars appearing red due to interstellar absorption; right is X-ray wavelengths, with the magnetar marked]] |
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The brightest |
The brightest O7–8V [[main sequence]] stars in Wd1 have [[Photometry (astronomy)|V-band photometric]] [[Apparent magnitude|magnitudes]] around 20.5, and therefore at visual wavelengths Wd1 is dominated by highly luminous post-Main Sequence stars (V-band magnitudes of 14.5–18, [[absolute magnitude]]s −7 to −10), along with less-luminous post-Main Sequence stars of [[Stellar classification#Yerkes spectral classification|luminosity class]] Ib and II (V-band magnitudes of 18–20). Due to the extremely high interstellar reddening towards Wd1, it is very difficult to observe in the U- and B-bands, and most observations are made in the R- or I-bands at the red end of the spectrum or in the [[infrared]]. Stars in the cluster are generally named using a classification introduced by Westerlund,<ref>{{Cite journal |last=Westerlund |first=B. E. |date=1987 |title=Photometry and spectroscopy of stars in the region of a highly reddened cluster in ARA |journal=Astronomy and Astrophysics |series=Supplement |issn=0365-0138 |volume=70 |issue=3 |pages=311–324 |bibcode=1987A&AS...70..311W }}</ref> although a separate naming convention is often used for the Wolf-Rayet stars.<ref name="crowther">{{Cite journal |last1=Crowther |first1=Paul A. |display-authors=etal |date=2006 |title=A census of the Wolf–Rayet content in Westerlund 1 from near-infrared imaging and spectroscopy |journal=[[Monthly Notices of the Royal Astronomical Society]] |volume=372 |issue=3 |pages=1407–1424 |doi=10.1111/j.1365-2966.2006.10952.x |arxiv=astro-ph/0608356 |bibcode=2006MNRAS.372.1407C|last2=Hadfield |first2=L. J. |last3=Clark |first3=J. S. |last4=Negueruela |first4=I. |last5=Vacca |first5=W. D. |doi-access=free |s2cid=10505573 }}</ref> |
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At X-ray wavelengths, Wd1 shows diffuse emission from interstellar gas and point emission from both high-mass, post-Main Sequence and low mass, pre-Main Sequence stars. The Westerlund 1 [[magnetar]] is the most luminous X-ray point source in the cluster, with the sgB[e] star W9, the (presumed) binary W30a and the Wolf–Rayet stars WR A and WR B all strong X-ray sources. Approximately 50 other X-ray point sources are associated with luminous optical counterparts. Finally, at [[radio astronomy|radio]] wavelengths the sgB[e] star W9 and red supergiants W20 and [[Westerlund 1 BKS AS|W26]] are strong radio sources, while the majority of the cool hypergiants and a few OB supergiants and Wolf–Rayet stars are also detected. |
At X-ray wavelengths, Wd1 shows diffuse emission from interstellar gas and point emission from both high-mass, post-Main Sequence and low mass, pre-Main Sequence stars. The Westerlund 1 [[magnetar]] is the most luminous X-ray point source in the cluster, with the sgB[e] star W9, the (presumed) binary W30a and the Wolf–Rayet stars WR A and WR B all strong X-ray sources. Approximately 50 other X-ray point sources are associated with luminous optical counterparts. Finally, at [[radio astronomy|radio]] wavelengths the sgB[e] star W9 and red supergiants W20 and [[Westerlund 1 BKS AS|W26]] are strong radio sources, while the majority of the cool hypergiants and a few OB supergiants and Wolf–Rayet stars are also detected. |
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==Age and evolutionary state== |
==Age and evolutionary state== |
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[[File:Artist’s impression of the magnetar in the star cluster Westerlund 1.jpg|left|thumb|upright=1.2|Artist's impression of the [[magnetar]] [[CXOU J164710.2-455216]] in the star cluster Westerlund 1 {{small|(ESO/L. Calçada)}}]] |
[[File:Artist’s impression of the magnetar in the star cluster Westerlund 1.jpg|left|thumb|upright=1.2|Artist's impression of the [[magnetar]] [[CXOU J164710.2-455216]] in the star cluster Westerlund 1 {{small|(ESO/L. Calçada)}}]] |
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The age of Wd1 is estimated at 4–5 [[Myr]] from comparison of the population of evolved stars with models of [[stellar evolution]]. The presence of significant numbers of both Wolf–Rayet stars ''and'' red and yellow supergiants in Wd1 represents a strong constraint on the age: theory suggests that red supergiants will not form until around 4 Myr as the most massive stars do not go through a red supergiant phase, while the Wolf–Rayet population declines sharply after 5 Myr. This range of ages is broadly consistent with infra-red observations of Wd1 that reveal the presence of [[Stellar classification#Class O|late-O]] main sequence stars, although a lower age of around 3.5 Myr has been suggested from observations of lower-mass stars in Wd1.<ref name="brandner">{{Cite journal | |
The age of Wd1 is estimated at 4–5 [[Myr]] from comparison of the population of evolved stars with models of [[stellar evolution]]. The presence of significant numbers of both Wolf–Rayet stars ''and'' red and yellow supergiants in Wd1 represents a strong constraint on the age: theory suggests that red supergiants will not form until around 4 Myr as the most massive stars do not go through a red supergiant phase, while the Wolf–Rayet population declines sharply after 5 Myr. This range of ages is broadly consistent with infra-red observations of Wd1 that reveal the presence of [[Stellar classification#Class O|late-O]] main sequence stars, although a lower age of around 3.5 Myr has been suggested from observations of lower-mass stars in Wd1.<ref name="brandner">{{Cite journal |last1=Brandner |first1=W. |display-authors=etal |date=2008 |title=Intermediate to low-mass stellar content of Westerlund 1 |journal=Astronomy & Astrophysics |volume=478 |issue=1 |pages=137–149 |doi=10.1051/0004-6361:20077579 |arxiv=0711.1624 |bibcode=2008A&A...478..137B|last2=Clark |first2=J. S. |last3=Stolte |first3=A. |last4=Waters |first4=R. |last5=Negueruela |first5=I. |last6=Goodwin |first6=S. P. |s2cid=15778583 }}</ref> |
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[[File:Comet-like stars Westerlund 1.tif|thumb|Comet-like stars in Westerlund 1 |
[[File:Comet-like stars Westerlund 1.tif|thumb|Comet-like stars in Westerlund 1<ref>{{cite web |title=Comet-like stars |url=https://www.eso.org/public/images/potw1849a/ |website=www.eso.org |access-date=3 December 2018}}</ref>]] |
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If Wd1 formed stars with a typical [[initial mass function]] then the cluster would have originally contained a significant number of very massive stars, such as those currently observed in the younger [[Arches Cluster|Arches cluster]]. Current estimates of the age of Wd1 are greater than the lifetimes of these stars, and stellar evolution models suggest that there would already have been 50–150 [[supernova]]e in Wd1, with a supernova rate of approximately one per 10,000 years over the last million years. However, to date only one definitive supernova remnant has been detected—the Westerlund 1 magnetar—and the lack of other [[compact object]]s and [[X-ray binary#High-mass X-ray binary|high-mass X-ray binaries]] is puzzling. A number of suggestions have been put forward, including high supernova [[Supernova#Asymmetry|kick velocities]] that disrupt binary systems, the formation of slowly accreting (and therefore undetectable) stellar mass [[black hole]]s, or binary systems in which both objects are now compact objects, but the problem has yet to be resolved. |
If Wd1 formed stars with a typical [[initial mass function]] then the cluster would have originally contained a significant number of very massive stars, such as those currently observed in the younger [[Arches Cluster|Arches cluster]]. Current estimates of the age of Wd1 are greater than the lifetimes of these stars, and stellar evolution models suggest that there would already have been 50–150 [[supernova]]e in Wd1, with a supernova rate of approximately one per 10,000 years over the last million years. However, to date only one definitive supernova remnant has been detected—the Westerlund 1 magnetar—and the lack of other [[compact object]]s and [[X-ray binary#High-mass X-ray binary|high-mass X-ray binaries]] is puzzling. A number of suggestions have been put forward, including high supernova [[Supernova#Asymmetry|kick velocities]] that disrupt binary systems, the formation of slowly accreting (and therefore undetectable) stellar mass [[black hole]]s, or binary systems in which both objects are now compact objects, but the problem has yet to be resolved. |
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As the stars in Westerlund 1 have the same age, composition and distance, the cluster represents an ideal environment for understanding the evolution of massive stars. The simultaneous presence of stars evolving on to and off of the Main Sequence presents a robust test for stellar evolution models, which are also currently unable to correctly predict the observed distribution of Wolf–Rayet subtypes in Westerlund 1.<ref name="negueruela">{{Cite journal | |
As the stars in Westerlund 1 have the same age, composition and distance, the cluster represents an ideal environment for understanding the evolution of massive stars. The simultaneous presence of stars evolving on to and off of the Main Sequence presents a robust test for stellar evolution models, which are also currently unable to correctly predict the observed distribution of Wolf–Rayet subtypes in Westerlund 1.<ref name="negueruela">{{Cite journal |last1=Negueruela |first1=Ignacio |display-authors=etal |date=2007 |title=Westerlund 1 as a Template for Massive Star Evolution |journal=Proceedings of the International Astronomical Union |volume=3 |pages=301–306 |doi=10.1017/S1743921308020620 |arxiv=0802.4168|last2=Clark |first2=J. Simon |last3=Hadfield |first3=Lucy J. |last4=Crowther |first4=Paul A. |bibcode=2008IAUS..250..301N |s2cid=10747013 }}</ref> |
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==Binary fraction== |
==Binary fraction== |
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A number of lines of evidence point to a high binary fraction amongst the high-mass stars in Wd1. Some massive binaries are detected directly |
A number of lines of evidence point to a high binary fraction amongst the high-mass stars in Wd1. Some massive binaries are detected directly |
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through photometry<ref name="bonanos">{{Cite journal |last=Bonanos |first=Alceste Z. |date=2007 |title=Variability of Young Massive Stars in the Galactic Super Star Cluster Westerlund 1 |journal=Astronomical Journal |volume=133 |issue=6 |pages=2696–2708 |doi=10.1086/518093 |bibcode=2007AJ....133.2696B |arxiv = astro-ph/0702614 }}</ref> and [[radial velocity]]<ref name="ritchie">{{Cite journal | |
through photometry<ref name="bonanos">{{Cite journal |last=Bonanos |first=Alceste Z. |date=2007 |title=Variability of Young Massive Stars in the Galactic Super Star Cluster Westerlund 1 |journal=Astronomical Journal |volume=133 |issue=6 |pages=2696–2708 |doi=10.1086/518093 |bibcode=2007AJ....133.2696B |arxiv = astro-ph/0702614 |s2cid=119074868 }}</ref> and [[radial velocity]]<ref name="ritchie">{{Cite journal |last1=Ritchie |first1=B. W. |display-authors=etal |date=2009 |title=A VLT/FLAMES survey for massive binaries in Westerlund 1: I. first observations of luminous evolved stars |journal= Astronomy and Astrophysics|volume=507 |issue=3 |pages=1585 |doi= 10.1051/0004-6361/200912686|arxiv=0909.3815|bibcode = 2009A&A...507.1585R |last2=Clark |first2=J. S. |last3=Negueruela |first3=I. |last4=Crowther |first4=P. A. |s2cid=197460709 }}</ref> observations, while many others are inferred through secondary characteristics (such as high X-ray luminosity, non-thermal radio spectra and excess infra-red emission) that are typical of colliding-wind binaries or dust-forming Wolf–Rayet stars. Overall binary fractions of 70% for the Wolf–Rayet population<ref name="crowther" /> and in excess of 40% for the OB supergiants are currently estimated, although both may be incomplete.<ref name="ritchie" /> |
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==Members== |
==Members== |
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| ⚫ | As well as documented members of the cluster, the [[luminous blue variable]] [[MN44]] is thought to be a [[runaway star]] ejected from Westerlund 1 four to five million years ago.<ref name=gvaramadze>{{cite journal|doi=10.3847/2515-5172/aaf23d|title=MN44: A Luminous Blue Variable Running Away from Westerlund 1|journal=Research Notes of the AAS|volume=2|issue=4|pages=214|year=2018|last1=Gvaramadze|first1=V. V.|bibcode=2018RNAAS...2..214G|arxiv=1811.07899|s2cid=119237114 |doi-access=free }}</ref> |
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{{Expand section|date=March 2018}} |
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| ⚫ | As well as documented members of the cluster, the [[luminous blue variable]] [[MN44]] is thought to be a [[runaway star]] ejected from Westerlund 1 four to five million years ago.<ref name=gvaramadze>{{cite journal|doi=10.3847/2515-5172/aaf23d|title=MN44: A Luminous Blue Variable Running Away from Westerlund 1|journal=Research Notes of the AAS|volume=2|issue=4|pages=214|year=2018|last1=Gvaramadze|first1=V. V.|bibcode=2018RNAAS...2..214G|arxiv=1811.07899}}</ref> |
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{| class="wikitable sortable" |
{| class="wikitable sortable" |
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! Designation !! [[Right ascension]] !! [[Declination]] !! Object type !! Spectral type !! Luminosity ({{solar luminosity}}) !! Temperature (K) |
! Designation !! [[Right ascension]] !! [[Declination]] !! Object type !! Spectral type !! Luminosity ({{solar luminosity}}) !! Temperature (K) |
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!Radius ({{Solar radius}}) |
!Radius ({{Solar radius}}) |
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| [[Westerlund 1-2a|W2a]]<ref name=clark/> || {{nowrap|{{RA|16|46|59.7}}}} || {{nowrap|{{DEC|-45|50|51.1}}}} || [[Blue supergiant]] || O9.5 Ia |
| [[Westerlund 1-2a|W2a]]<ref name=clark/> || {{nowrap|{{RA|16|46|59.7}}}} || {{nowrap|{{DEC|-45|50|51.1}}}} || [[Blue supergiant]] || O9.5 Ia – B0.5 Ia |
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| [[Westerlund 1-4|W4]]<ref name=clark/> || {{nowrap|{{RA|16|47|01.42}}}} || {{nowrap|{{DEC|-45|50|37.1}}}} || [[Yellow hypergiant]] || G0 Ia<sup>+</sup> |
| [[Westerlund 1-4|W4]]<ref name=clark/> || {{nowrap|{{RA|16|47|01.42}}}} || {{nowrap|{{DEC|-45|50|37.1}}}} || [[Yellow hypergiant]] || G0 Ia<sup>+</sup> – F2 Ia<sup>+</sup> |
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| [[Westerlund 1-5|W5]]<ref name="Negueruela, Clark, Ritchie, 2010"/> || {{nowrap|{{RA|16|47|02.97}}}} || {{nowrap|{{DEC|-45|50|19.5}}}} || [[Hypergiant|Blue hypergiant]] |
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| [[Westerlund 1-8b|W8b]]<ref name="Negueruela, Clark, Ritchie, 2010">{{Cite journal|last1=Negueruela|first1=Ignacio|last2=Clark|first2=J. Simon|last3=Ritchie|first3=Ben W.|title=The population of OB supergiants in the starburst cluster Westerlund 1|journal=Astronomy and Astrophysics|volume=516|issue=78|pages=A78|arxiv=1003.5204|date=2010|doi=10.1051/0004-6361/201014032|bibcode=2010A&A...516A..78N}}</ref> || {{nowrap|{{RA|16|47|04.95}}}} || {{nowrap|{{DEC|-45|50|26.7}}}} || [[Blue |
| [[Westerlund 1-8b|W8b]]<ref name="Negueruela, Clark, Ritchie, 2010">{{Cite journal|last1=Negueruela|first1=Ignacio|last2=Clark|first2=J. Simon|last3=Ritchie|first3=Ben W.|title=The population of OB supergiants in the starburst cluster Westerlund 1|journal=Astronomy and Astrophysics|volume=516|issue=78|pages=A78|arxiv=1003.5204|date=2010|doi=10.1051/0004-6361/201014032|bibcode=2010A&A...516A..78N|s2cid=230718}}</ref> || {{nowrap|{{RA|16|47|04.95}}}} || {{nowrap|{{DEC|-45|50|26.7}}}} || [[Hypergiant|Blue hypergiant]] || B1-5Ia |
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| [[Westerlund 1-13|W13]]<ref name="Clark, Ritchie, 2010">{{cite journal|last1=Negueruela|first1=I.|last2=Clark|first2=J. S.|last3=Ritchie|first3=B. W.|title=The population of OB supergiants in the starburst cluster Westerlund 1|journal=Astronomy & Astrophysics|date=2010|volume=516|page=3|doi=10.1051/0004-6361/201014032|arxiv=1003.5204|bibcode=2010A&A...516A..78N}}</ref><ref name="ritchie"/> || {{nowrap|{{RA|16|47|06.45}}}} || {{nowrap|{{DEC|-45|50|26.0}}}} || [[Eclipsing binary]] || B0.5 Ia<sup>+</sup> |
| [[Westerlund 1-13|W13]]<ref name="Clark, Ritchie, 2010">{{cite journal|last1=Negueruela|first1=I.|last2=Clark|first2=J. S.|last3=Ritchie|first3=B. W.|title=The population of OB supergiants in the starburst cluster Westerlund 1|journal=Astronomy & Astrophysics|date=2010|volume=516|page=3|doi=10.1051/0004-6361/201014032|arxiv=1003.5204|bibcode=2010A&A...516A..78N|s2cid=230718}}</ref><ref name="ritchie"/> || {{nowrap|{{RA|16|47|06.45}}}} || {{nowrap|{{DEC|-45|50|26.0}}}} || [[Eclipsing binary]] || B0.5 Ia<sup>+</sup> + OB |
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| [[Westerlund 1-26|W26]]<ref name=clark/> || {{nowrap|{{RA|16|47|05.40}}}} || {{nowrap|{{DEC|-45|50|36.5}}}} || [[Red |
| [[Westerlund 1-26|W26]]<ref name=clark/> || {{nowrap|{{RA|16|47|05.40}}}} || {{nowrap|{{DEC|-45|50|36.5}}}} || [[Red supergiant]] || M2-6Ia<ref name=clark2011>{{cite journal|doi=10.1051/0004-6361/201116990|title=A VLT/FLAMES survey for massive binaries in Westerlund 1|journal=Astronomy & Astrophysics|volume=531|pages=A28|year=2011|last1=Clark|first1=J. S.|last2=Ritchie|first2=B. W.|last3=Negueruela|first3=I.|last4=Crowther|first4=P. A.|last5=Damineli|first5=A.|last6=Jablonski|first6=F. J.|last7=Langer|first7=N.|bibcode=2011A&A...531A..28C|arxiv = 1105.0776 |s2cid=119299122|url=http://oro.open.ac.uk/30687/1/1105.0776v1.pdf}}</ref> || 380,000<ref name=wright>{{cite journal|last1=Wright|first1=N. J.|last2=Wesson|first2=R.|last3=Drew|first3=J. E.|last4=Barentsen|first4=G.|last5=Barlow|first5=M. J.|last6=Walsh|first6=J. R.|last7=Zijlstra|first7=A.|last8=Drake|first8=J. J.|last9=Eisloffel|first9=J.|last10=Farnhill|first10=H. J.|title=The ionized nebula surrounding the red supergiant W26 in Westerlund 1|journal=Monthly Notices of the Royal Astronomical Society: Letters|date=16 October 2013|volume=437|issue=1|pages=L1–L5|doi=10.1093/mnrasl/slt127|doi-access=free |arxiv = 1309.4086 |bibcode = 2014MNRAS.437L...1W |s2cid=14889377}}</ref> – 1,100,000<ref name=fok/> || 3,600<ref name=mackey>{{cite journal|arxiv=1508.07003|doi=10.1051/0004-6361/201526159|title=Cold gas in hot star clusters: The wind from the red supergiant W26 in Westerlund 1|journal=Astronomy & Astrophysics|volume=582|pages=A24|year=2015|last1=MacKey|first1=Jonathan|last2=Castro|first2=Norberto|last3=Fossati|first3=Luca|last4=Langer|first4=Norbert|bibcode=2015A&A...582A..24M|s2cid=54683876}}</ref> – 3,700<ref name=fok>{{cite journal|bibcode=2012ApJ...760...65F|arxiv=1209.6427|title=Maser Observations of Westerlund 1 and Comprehensive Considerations on Maser Properties of Red Supergiants Associated with Massive Clusters|journal=The Astrophysical Journal|volume=760|issue=1|pages=65|last1=Fok|first1=Thomas K. T.|last2=Nakashima|first2=Jun-Ichi|last3=Yung|first3=Bosco H. K.|last4=Hsia|first4=Chih-Hao|last5=Deguchi|first5=Shuji|year=2012|doi=10.1088/0004-637X/760/1/65|s2cid=53393926}}</ref> |
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|1,530<ref name="wright" />−2,550<ref name="fok" />,1,165–1,221<ref name=paulo2018>{{cite thesis |doi=10.11606/D.14.2019.tde-12092018-161841 |title=The Red Supergiants in the Supermassive Stellar Cluster Westerlund 1 |year=2019 |last1=Arévalo |first1=Aura |doi-access=free }}</ref> |
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|1,530<ref name="wright" />-2,550<ref name="fok" /> |
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| [[Westerlund 1-32|W32]]<ref name=clark/> || {{nowrap|{{RA|16|47|03.67}}}} || {{nowrap|{{DEC|-45|50|43.5}}}} || [[Yellow hypergiant]] || || || |
| [[Westerlund 1-32|W32]]<ref name=clark/> || {{nowrap|{{RA|16|47|03.67}}}} || {{nowrap|{{DEC|-45|50|43.5}}}} || [[Yellow hypergiant]] || || || |
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| [[Westerlund 1-33|W33]]<ref name=clark/> || {{nowrap|{{RA|16|47|04.12}}}} || {{nowrap|{{DEC|-45|50|48.3}}}} || [[Blue hypergiant]] || || || |
| [[Westerlund 1-33|W33]]<ref name=clark/> || {{nowrap|{{RA|16|47|04.12}}}} || {{nowrap|{{DEC|-45|50|48.3}}}} || [[Blue hypergiant]] || || || || |
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| [[Westerlund 1-36|W36]]<ref>{{cite journal | arxiv=2210.04985 | doi=10.1093/mnras/stac2927 | bibcode=2022MNRAS.517.3749R | title=Distance and age of the massive stellar cluster Westerlund 1 – II. The eclipsing binary W36 | year=2022 | last1=Rocha | first1=Danilo F. | last2=Almeida | first2=Leonardo A. | last3=Damineli | first3=Augusto | last4=Navarete | first4=Felipe | last5=Abdul-Masih | first5=Michael | last6=Mace | first6=Gregory N. | journal=Monthly Notices of the Royal Astronomical Society | volume=517 | issue=3 | pages=3749–3762 | doi-access=free }}</ref> || {{nowrap|{{RA|16|47|05.08}}}} || {{nowrap|{{DEC|-45|50|55.1}}}} || [[Eclipsing binary]] || O6.5III + O9.5 IV || 275,000 + 89,000<!-- log(L/Lsol) = 5.44 and 4.95 --> || 12.69 + 10.46 || |
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| [[Westerlund 1-75|W75]]<ref name=clark2009/> || {{nowrap|{{RA|16|47|08.93}}}} || {{nowrap|{{DEC|-45|49|58.4}}}} || [[Red supergiant]] || || 68,000<ref name=fok/> || 3,600<ref name=fok/> |
| [[Westerlund 1-75|W75]]<ref name=clark2009/> || {{nowrap|{{RA|16|47|08.93}}}} || {{nowrap|{{DEC|-45|49|58.4}}}} || [[Red supergiant]] || || 68,000<ref name=fok/> || 3,600<ref name=fok/> |
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|668<ref name="fok" /> |
|668<ref name="fok" /> |
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| [[Westerlund 1-237|W237]]<ref name=clark/> || {{nowrap|{{RA|16|47|03.09}}}} || {{nowrap|{{DEC|-45|52|18.8}}}} || [[Red supergiant]] || || 234,000<ref name=fok/>|| 3, |
| [[Westerlund 1-237|W237]]<ref name=clark/> || {{nowrap|{{RA|16|47|03.09}}}} || {{nowrap|{{DEC|-45|52|18.8}}}} || [[Red supergiant]] || || 234,000<ref name=fok/>|| 3,605<ref name=fok/> |
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|1,245<ref name="fok" /> |
|1,245<ref name="fok" /> |
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| [[Westerlund 1-243|W243]]<ref name=clark/> || {{nowrap|{{RA|16|47|07.55}}}} || {{nowrap|{{DEC|-45|52|28.5}}}} || [[Luminous blue variable]] || LBV || || |
| [[Westerlund 1-243|W243]]<ref name=clark/> || {{nowrap|{{RA|16|47|07.55}}}} || {{nowrap|{{DEC|-45|52|28.5}}}} || [[Luminous blue variable]] || LBV || || |
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| Line 152: | Line 160: | ||
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| WR 77a<ref name="Negueruela, Clark, 2005"/> || {{nowrap|{{RA|16|46|55.4}}}} || {{nowrap|{{DEC|-45|51|34}}}} || [[Wolf–Rayet star]] || |
| WR 77a<ref name="Negueruela, Clark, 2005"/> || {{nowrap|{{RA|16|46|55.4}}}} || {{nowrap|{{DEC|-45|51|34}}}} || [[Wolf–Rayet star]] || WN6–7 |
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| WR 77aa<ref name="Crowther, Hadfield, Clark, Negueruela, Vacca">{{cite journal|last1=Crowther|first1=Paul A.|last2=Hadfield|first2=L. J.|last3=Clark|first3=J. S.|last4=Negueruela|first4=I.|last5=Vacca|first5=W. D.|title=A census of the Wolf–Rayet content in Westerlund 1 from near-infrared imaging and spectroscopy|journal=Monthly Notices of the Royal Astronomical Society|date=2006-09-29|volume=372|issue=3|page=1411|doi=10.1111/j.1365-2966.2006.10952.x|arxiv=astro-ph/0608356|bibcode=2006MNRAS.372.1407C}}</ref> || {{nowrap|{{RA|16|46|46.3}}}} || {{nowrap|{{DEC|-45|47|58}}}} || [[Wolf–Rayet star]] || WC9d |
| WR 77aa<ref name="Crowther, Hadfield, Clark, Negueruela, Vacca">{{cite journal|last1=Crowther|first1=Paul A.|last2=Hadfield|first2=L. J.|last3=Clark|first3=J. S.|last4=Negueruela|first4=I.|last5=Vacca|first5=W. D.|title=A census of the Wolf–Rayet content in Westerlund 1 from near-infrared imaging and spectroscopy|journal=Monthly Notices of the Royal Astronomical Society|date=2006-09-29|volume=372|issue=3|page=1411|doi=10.1111/j.1365-2966.2006.10952.x|doi-access=free |arxiv=astro-ph/0608356|bibcode=2006MNRAS.372.1407C|s2cid=10505573}}</ref> || {{nowrap|{{RA|16|46|46.3}}}} || {{nowrap|{{DEC|-45|47|58}}}} || [[Wolf–Rayet star]] || WC9d |
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| WR 77e<ref name="Negueruela, Clark, 2005"/> || {{nowrap|{{RA|16|47|01.67}}}} || {{nowrap|{{DEC|-45|51|19.9}}}} || [[Wolf–Rayet star]] || |
| WR 77e<ref name="Negueruela, Clark, 2005"/> || {{nowrap|{{RA|16|47|01.67}}}} || {{nowrap|{{DEC|-45|51|19.9}}}} || [[Wolf–Rayet star]] || WN6–8 |
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| WR 77g<ref name="Negueruela, Clark, 2005"/> || {{nowrap|{{RA|16|47|03.1}}}} || {{nowrap|{{DEC|-45|50|43}}}} || [[Wolf–Rayet star]] || WC7 |
| WR 77g<ref name="Negueruela, Clark, 2005"/> || {{nowrap|{{RA|16|47|03.1}}}} || {{nowrap|{{DEC|-45|50|43}}}} || [[Wolf–Rayet star]] || WC7 |
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| WR 77i<ref name="Negueruela, Clark, 2005"/> || {{nowrap|{{RA|16|47|04.02}}}} || {{nowrap|{{DEC|-45|51|25.2}}}} || [[Wolf–Rayet star]] || |
| WR 77i<ref name="Negueruela, Clark, 2005"/> || {{nowrap|{{RA|16|47|04.02}}}} || {{nowrap|{{DEC|-45|51|25.2}}}} || [[Wolf–Rayet star]] || WN6–8 |
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| WR 77o, W14c<ref name="Negueruela, Clark, 2005"/> || {{nowrap|{{RA|16|47|06.0}}}} || {{nowrap|{{DEC|-45|15|22}}}} || [[Wolf–Rayet star]] || WN7o<ref>{{Cite journal|last1=Koumpia|first1=E. |last2=Bonanos|first2=A. Z.|date=2012|title=The Fundamental Parameters of Four Massive Eclipsing Binaries in Westerlund 1 |journal=Astronomy & Astrophysics |volume=547 |pages=A30 |arxiv=1205.1369 |doi=10.1051/0004-6361/201219465 |bibcode=2012A&A...547A..30K}}</ref> |
| WR 77o, W14c<ref name="Negueruela, Clark, 2005"/> || {{nowrap|{{RA|16|47|06.0}}}} || {{nowrap|{{DEC|-45|15|22}}}} || [[Wolf–Rayet star]] || WN7o<ref>{{Cite journal|last1=Koumpia|first1=E. |last2=Bonanos|first2=A. Z.|date=2012|title=The Fundamental Parameters of Four Massive Eclipsing Binaries in Westerlund 1 |journal=Astronomy & Astrophysics |volume=547 |pages=A30 |arxiv=1205.1369 |doi=10.1051/0004-6361/201219465 |bibcode=2012A&A...547A..30K|s2cid=118604150 }}</ref> |
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| WR 77q<ref name="Negueruela, Clark, 2005"/> || {{nowrap|{{RA|16|47|06.24}}}} || {{nowrap|{{DEC|-45|51|26.5}}}} || [[Wolf–Rayet star]] || |
| WR 77q<ref name="Negueruela, Clark, 2005"/> || {{nowrap|{{RA|16|47|06.24}}}} || {{nowrap|{{DEC|-45|51|26.5}}}} || [[Wolf–Rayet star]] || WN6–8 |
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| WR 77r<ref name="Negueruela, Clark, 2005"/> || {{nowrap|{{RA|16|47|07.6}}}} || {{nowrap|{{DEC|-45|52|36}}}} || [[Wolf–Rayet star]] || WN6 |
| WR 77r<ref name="Negueruela, Clark, 2005"/> || {{nowrap|{{RA|16|47|07.6}}}} || {{nowrap|{{DEC|-45|52|36}}}} || [[Wolf–Rayet star]] || WN6 |
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| WR 77s, W72<ref name="Negueruela, Clark, 2005">{{cite journal|last1=Negueruela|first1=I.|last2=Clark|first2=J. S.|title=Further |
| WR 77s, W72<ref name="Negueruela, Clark, 2005">{{cite journal|last1=Negueruela|first1=I.|last2=Clark|first2=J. S.|title=Further Wolf–Rayet stars in the starburst cluster Westerlund 1|journal=Astronomy & Astrophysics|date=2005|volume=436|issue=2|pages=541|doi=10.1051/0004-6361:20052699|bibcode=2005A&A...436..541N|arxiv=astro-ph/0503303|s2cid=1755956}}</ref> || {{nowrap|{{RA|16|47|08.32}}}} || {{nowrap|{{DEC|-45|50|45.5}}}} || [[Wolf–Rayet star]] || WN6o<ref name="crowther" /> |
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| WR 77sa<ref name="crowther" /> || {{nowrap|{{RA|16|47|07.58}}}} || {{nowrap|{{DEC|-45|49|22.2}}}} || [[Wolf–Rayet star]] || WN6h |
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| WR 77sb<ref name="crowther" /> || {{nowrap|{{RA|16|47|07.66}}}} || {{nowrap|{{DEC|-45|52|35.9}}}} || [[Wolf–Rayet star]] || WN6o |
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| WR 77sc, W72<ref name="crowther" /> || {{nowrap|{{RA|16|47|08.32}}}} || {{nowrap|{{DEC|-45|50|45.5}}}} || [[Wolf–Rayet star]] || WN7b |
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| WR 77sd<ref name="crowther" /> || {{nowrap|{{RA|16|47|14.1}}}} || {{nowrap|{{DEC|-45|48|32}}}} || [[Wolf–Rayet star]] || WN4–5 |
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==References== |
==References== |
||
{{Reflist |
{{Reflist|refs= |
||
<ref name=clark2009>{{cite journal|doi=10.1051/0004-6361/200913820|arxiv=1003.5107|title=A serendipitous survey for variability amongst the massive stellar population of Westerlund 1|journal=Astronomy and Astrophysics|volume=514|pages=A87|year=2010|last1=Clark|first1=J. S|last2=Ritchie|first2=B. W|last3=Negueruela|first3=I|bibcode=2010A&A...514A..87C}}</ref> |
<ref name=clark2009>{{cite journal|doi=10.1051/0004-6361/200913820|arxiv=1003.5107|title=A serendipitous survey for variability amongst the massive stellar population of Westerlund 1|journal=Astronomy and Astrophysics|volume=514|pages=A87|year=2010|last1=Clark|first1=J. S|last2=Ritchie|first2=B. W|last3=Negueruela|first3=I|bibcode=2010A&A...514A..87C|s2cid=14780809}}</ref> |
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* [http://aladin.u-strasbg.fr/AladinPreview?-c=16+47+04.00-45+51+04.9&ident=ESO+277-12&submit=Aladin+previewer Image of Westerlund 1] |
* [http://aladin.u-strasbg.fr/AladinPreview?-c=16+47+04.00-45+51+04.9&ident=ESO+277-12&submit=Aladin+previewer Image of Westerlund 1] |
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* [http://chandra.harvard.edu/photo/2005/wd1/ Neutron star found where black hole expected] |
* [http://chandra.harvard.edu/photo/2005/wd1/ Neutron star found where black hole expected] |
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{{Ara (constellation)}} |
{{Ara (constellation)}} |
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{{Authority control}} |
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{{DEFAULTSORT:Westerlund 1}} |
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[[Category:Open clusters]] |
[[Category:Open clusters]] |
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[[Category:Super star clusters]] |
[[Category:Super star clusters]] |
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Latest revision as of 15:16, 29 September 2024
| Westerlund 1 | |
|---|---|
 Credit: ESO/VPHAS+ Survey/N. Wright | |
| Observation data (J2000 epoch) | |
| Right ascension | 16h 47m 04.0s[1] |
| Declination | −45° 51′ 04.9″[1] |
| Distance | 3.78+0.56 −0.46[2] (2.6[3] – 4.23[4]) kpc |
| Physical characteristics | |
| Mass | 63,000[5] M☉ |
| Radius | 3.26 ly[5] |
| Estimated age | 3.50 Myr[5] |
| Other designations | Ara Cluster, Westerlund 1, ESO 277-12, C 1644-457, VDBH 197 |
| Associations | |
| Constellation | Ara |
Westerlund 1 (abbreviated Wd1, sometimes called Ara Cluster[6]) is a compact young super star cluster about 3.8 kpc (12,000 ly) away from Earth. It is thought to be the most massive young star cluster in the Milky Way,[4] and was discovered by Bengt Westerlund in 1961[7] but remained largely unstudied for many years due to high interstellar absorption in its direction. In the future, it will probably evolve into a globular cluster.[8]
The cluster contains a large number of rare, evolved, high-mass stars, including: 6 yellow hypergiants, 4 red supergiants including Westerlund 1-26, one of the largest known stars, 24 Wolf-Rayet stars, a luminous blue variable, many OB supergiants, and an unusual supergiant sgB[e] star which has been proposed to be the remnant of a recent stellar merger.[9] In addition, X-ray observations have revealed the presence of the anomalous X-ray pulsar CXO J164710.20-455217, a slow rotating neutron star that must have formed from a high-mass progenitor star.[10] Westerlund 1 is believed to have formed in a single burst of star formation, implying the constituent stars have similar ages and compositions.
Aside from hosting some of the most massive and least-understood stars in our galaxy, Westerlund 1 is useful as a relatively nearby, easy to observe super star cluster that can help astronomers determine what occurs within extragalactic super star clusters.
Observations
[edit]
The brightest O7–8V main sequence stars in Wd1 have V-band photometric magnitudes around 20.5, and therefore at visual wavelengths Wd1 is dominated by highly luminous post-Main Sequence stars (V-band magnitudes of 14.5–18, absolute magnitudes −7 to −10), along with less-luminous post-Main Sequence stars of luminosity class Ib and II (V-band magnitudes of 18–20). Due to the extremely high interstellar reddening towards Wd1, it is very difficult to observe in the U- and B-bands, and most observations are made in the R- or I-bands at the red end of the spectrum or in the infrared. Stars in the cluster are generally named using a classification introduced by Westerlund,[11] although a separate naming convention is often used for the Wolf-Rayet stars.[12]
At X-ray wavelengths, Wd1 shows diffuse emission from interstellar gas and point emission from both high-mass, post-Main Sequence and low mass, pre-Main Sequence stars. The Westerlund 1 magnetar is the most luminous X-ray point source in the cluster, with the sgB[e] star W9, the (presumed) binary W30a and the Wolf–Rayet stars WR A and WR B all strong X-ray sources. Approximately 50 other X-ray point sources are associated with luminous optical counterparts. Finally, at radio wavelengths the sgB[e] star W9 and red supergiants W20 and W26 are strong radio sources, while the majority of the cool hypergiants and a few OB supergiants and Wolf–Rayet stars are also detected.
Age and evolutionary state
[edit]
The age of Wd1 is estimated at 4–5 Myr from comparison of the population of evolved stars with models of stellar evolution. The presence of significant numbers of both Wolf–Rayet stars and red and yellow supergiants in Wd1 represents a strong constraint on the age: theory suggests that red supergiants will not form until around 4 Myr as the most massive stars do not go through a red supergiant phase, while the Wolf–Rayet population declines sharply after 5 Myr. This range of ages is broadly consistent with infra-red observations of Wd1 that reveal the presence of late-O main sequence stars, although a lower age of around 3.5 Myr has been suggested from observations of lower-mass stars in Wd1.[1]
If Wd1 formed stars with a typical initial mass function then the cluster would have originally contained a significant number of very massive stars, such as those currently observed in the younger Arches cluster. Current estimates of the age of Wd1 are greater than the lifetimes of these stars, and stellar evolution models suggest that there would already have been 50–150 supernovae in Wd1, with a supernova rate of approximately one per 10,000 years over the last million years. However, to date only one definitive supernova remnant has been detected—the Westerlund 1 magnetar—and the lack of other compact objects and high-mass X-ray binaries is puzzling. A number of suggestions have been put forward, including high supernova kick velocities that disrupt binary systems, the formation of slowly accreting (and therefore undetectable) stellar mass black holes, or binary systems in which both objects are now compact objects, but the problem has yet to be resolved.
As the stars in Westerlund 1 have the same age, composition and distance, the cluster represents an ideal environment for understanding the evolution of massive stars. The simultaneous presence of stars evolving on to and off of the Main Sequence presents a robust test for stellar evolution models, which are also currently unable to correctly predict the observed distribution of Wolf–Rayet subtypes in Westerlund 1.[14]
Binary fraction
[edit]A number of lines of evidence point to a high binary fraction amongst the high-mass stars in Wd1. Some massive binaries are detected directly through photometry[15] and radial velocity[16] observations, while many others are inferred through secondary characteristics (such as high X-ray luminosity, non-thermal radio spectra and excess infra-red emission) that are typical of colliding-wind binaries or dust-forming Wolf–Rayet stars. Overall binary fractions of 70% for the Wolf–Rayet population[12] and in excess of 40% for the OB supergiants are currently estimated, although both may be incomplete.[16]
Members
[edit]As well as documented members of the cluster, the luminous blue variable MN44 is thought to be a runaway star ejected from Westerlund 1 four to five million years ago.[17]
| Designation | Right ascension | Declination | Object type | Spectral type | Luminosity (L☉) | Temperature (K) | Radius (R☉) |
|---|---|---|---|---|---|---|---|
| W2a[9] | 16h 46m 59.7s | −45° 50′ 51.1″ | Blue supergiant | O9.5 Ia – B0.5 Ia | |||
| W4[9] | 16h 47m 01.42s | −45° 50′ 37.1″ | Yellow hypergiant | G0 Ia+ – F2 Ia+ | |||
| W5[18] | 16h 47m 02.97s | −45° 50′ 19.5″ | Blue hypergiant | ||||
| W6a[9] | 16h 47m 04.0s | −45° 50′ 21.0″ | Blue supergiant | ||||
| W7[9] | 16h 46m 03.62s | −45° 50′ 14.2″ | Blue hypergiant | ||||
| W8a[9] | 16h 47m 04.79s | −45° 50′ 24.9″ | Yellow hypergiant | ||||
| W8b[18] | 16h 47m 04.95s | −45° 50′ 26.7″ | Blue hypergiant | B1-5Ia | |||
| W9[9] | 16h 47m 04.14s | −45° 50′ 31.1″ | B[e] star | sgB[e] | |||
| W12a[9] | 16h 47m 02.21s | −45° 50′ 58.8″ | Yellow hypergiant | ||||
| W13[19][16] | 16h 47m 06.45s | −45° 50′ 26.0″ | Eclipsing binary | B0.5 Ia+ + OB | |||
| W16a[9] | 16h 47m 06.61s | −45° 50′ 42.1″ | Yellow hypergiant | ||||
| W20[9] | 16h 47m 04.70s | −45° 51′ 23.8″ | Red supergiant | 126,000[20] | 3,500[20] | 965[20] | |
| W26[9] | 16h 47m 05.40s | −45° 50′ 36.5″ | Red supergiant | M2-6Ia[21] | 380,000[22] – 1,100,000[20] | 3,600[23] – 3,700[20] | 1,530[22]−2,550[20],1,165–1,221[24] |
| W32[9] | 16h 47m 03.67s | −45° 50′ 43.5″ | Yellow hypergiant | ||||
| W33[9] | 16h 47m 04.12s | −45° 50′ 48.3″ | Blue hypergiant | ||||
| W36[25] | 16h 47m 05.08s | −45° 50′ 55.1″ | Eclipsing binary | O6.5III + O9.5 IV | 275,000 + 89,000 | 12.69 + 10.46 | |
| W75[26] | 16h 47m 08.93s | −45° 49′ 58.4″ | Red supergiant | 68,000[20] | 3,600[20] | 668[20] | |
| W237[9] | 16h 47m 03.09s | −45° 52′ 18.8″ | Red supergiant | 234,000[20] | 3,605[20] | 1,245[20] | |
| W243[9] | 16h 47m 07.55s | −45° 52′ 28.5″ | Luminous blue variable | LBV | |||
| W265[9] | 16h 47m 06.26s | −45° 49′ 23.7″ | Yellow hypergiant | ||||
| WR 77a[27] | 16h 46m 55.4s | −45° 51′ 34″ | Wolf–Rayet star | WN6–7 | |||
| WR 77aa[28] | 16h 46m 46.3s | −45° 47′ 58″ | Wolf–Rayet star | WC9d | |||
| WR 77b[27] | 16h 46m 59.9s | −45° 55′ 26″ | Wolf–Rayet star | WC8 | |||
| WR 77c[27] | 16h 47m 00.89s | −45° 51′ 20.9″ | Wolf–Rayet star | WNL | |||
| WR 77d, W57c[27] | 16h 47m 01.5s | −45° 51′ 45″ | Wolf–Rayet star | WN8 | |||
| WR 77e[27] | 16h 47m 01.67s | −45° 51′ 19.9″ | Wolf–Rayet star | WN6–8 | |||
| WR 77f, W5[27] | 16h 47m 02.97s | −45° 50′ 19.5″ | Wolf–Rayet star | WNVL | |||
| WR 77g[27] | 16h 47m 03.1s | −45° 50′ 43″ | Wolf–Rayet star | WC7 | |||
| WR 77h, W66[27] | 16h 47m 04.0s | −45° 51′ 37.5″ | Wolf–Rayet star | WC9 | |||
| WR 77i[27] | 16h 47m 04.02s | −45° 51′ 25.2″ | Wolf–Rayet star | WN6–8 | |||
| WR 77j, W44[27] | 16h 47m 04.20s | −45° 51′ 07.0″ | Wolf–Rayet star | WN9 | |||
| WR 77k[27] | 16h 47m 04.1s | −45° 51′ 20.0″ | Wolf–Rayet star | WC9 | |||
| WR 77l[27] | 16h 47m 04.40s | −45° 51′ 03.8″ | Wolf–Rayet star | WC8.5 | |||
| WR 77m, W239[27] | 16h 47m 05.21s | −45° 52′ 25.0″ | Wolf–Rayet star | WC9 | |||
| WR 77n[27] | 16h 47m 05.35s | −45° 51′ 05.0″ | Wolf–Rayet star | WN8 (uncertain) | |||
| WR 77o, W14c[27] | 16h 47m 06.0s | −45° 15′ 22″ | Wolf–Rayet star | WN7o[29] | |||
| WR 77p, W241[27] | 16h 47m 06.06s | −45° 52′ 08.3″ | Wolf–Rayet star | WC9 | |||
| WR 77q[27] | 16h 47m 06.24s | −45° 51′ 26.5″ | Wolf–Rayet star | WN6–8 | |||
| WR 77r[27] | 16h 47m 07.6s | −45° 52′ 36″ | Wolf–Rayet star | WN6 | |||
| WR 77s, W72[27] | 16h 47m 08.32s | −45° 50′ 45.5″ | Wolf–Rayet star | WN6o[12] | |||
| WR 77sa[12] | 16h 47m 07.58s | −45° 49′ 22.2″ | Wolf–Rayet star | WN6h | |||
| WR 77sb[12] | 16h 47m 07.66s | −45° 52′ 35.9″ | Wolf–Rayet star | WN6o | |||
| WR 77sc, W72[12] | 16h 47m 08.32s | −45° 50′ 45.5″ | Wolf–Rayet star | WN7b | |||
| WR 77sd[12] | 16h 47m 14.1s | −45° 48′ 32″ | Wolf–Rayet star | WN4–5 | |||
| CXOU J164710.2-455216[30] | 16h 47m 10.18s | −45° 52′ 16.7″ | anomalous X-ray pulsar |
References
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- ^ SIMBAD, CXOU J164710.2-455216
External links
[edit]
Wikimedia Commons has media related to Westerlund 1.
- "Cl Westerlund 1". SIMBAD. Centre de données astronomiques de Strasbourg.
- Artist’s impression of a magnetar X-ray satellites catch magnetar in gigantic stellar ‘hiccup’, ESA website, 2007
- Image of Westerlund 1
- Neutron star found where black hole expected
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