Westerlund 1

This article is about the super star cluster. For the red supergiant star, see Westerlund 1 W26.
Westerlund 1

Credit: ESO/VPHAS+ Survey/N. Wright
Observation data (J2000 epoch)
Right ascension16h 47m 04.0s[1]
Declination−45° 51′ 04.9″[1]
Distance3.78+0.56
−0.46[2] (2.6[3] – 4.23[4]) kpc
Physical characteristics
Mass63,000[5] M☉
Radius3.26 ly[5]
Estimated age3.50 Myr[5]
Other designationsAra Cluster, Westerlund 1, ESO 277-12, C 1644-457, VDBH 197
Associations
ConstellationAra
See also: Open cluster, List of open clusters

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.

  1. ^ a b Cite error: The named reference brandner was invoked but never defined (see the help page).
  2. ^ Parker, Richard J.; Crowther, Paul A.; Rate, Gemma (2020). "Unlocking Galactic Wolf–Rayet stars with Gaia DR2 – II. Cluster and association membership". Monthly Notices of the Royal Astronomical Society. 495: 1209–1226. arXiv:2005.02533. doi:10.1093/mnras/staa1290. S2CID 218516882.
  3. ^ Aghakhanloo, Mojgan; Murphy, Jeremiah W.; Smith, Nathan; Parejko, John; Díaz-Rodríguez, Mariangelly; Drout, Maria R.; Groh, Jose H.; Guzman, Joseph; Stassun, Keivan G. (2020-02-21). "Inferring the parallax of Westerlund 1 from Gaia DR2". Monthly Notices of the Royal Astronomical Society. 492 (2): 2497–2509. arXiv:1901.06582. Bibcode:2020MNRAS.492.2497A. doi:10.1093/mnras/stz3628. ISSN 0035-8711. S2CID 119465620.
  4. ^ a b Negueruela, I.; Alfaro, E. J.; Dorda, R.; Marco, A.; Maíz Apellániz, J.; González-Fernández, C. (2022). "Westerlund 1 under the light of Gaia EDR3: Distance, isolation, extent, and a hidden population". Astronomy & Astrophysics. 664: A146. arXiv:2204.00422. Bibcode:2022A&A...664A.146N. doi:10.1051/0004-6361/202142985. S2CID 247922758.
  5. ^ a b c Portegies Zwart, Simon F.; McMillan, Stephen L.W.; Gieles, Mark (2010). "Young Massive Star Clusters". Annual Review of Astronomy and Astrophysics. 48: 431–493. arXiv:1002.1961. Bibcode:2010ARA&A..48..431P. doi:10.1146/annurev-astro-081309-130834. S2CID 119207843.
  6. ^ Westerlund, B. E. (1968). "On the Extended Infrared Source in ARA". Astrophysical Journal. 154: L67. Bibcode:1968ApJ...154L..67W. doi:10.1086/180270.
  7. ^ Westerlund, B. (1961). "A Heavily Reddened Cluster in Ara". Astronomical Journal. 70: 57. Bibcode:1961AJ.....66T..57W. doi:10.1086/108585.
  8. ^ Gallagher & Grebel (2002). "Extragalactic Star Clusters: Speculations on the Future". Extragalactic Star Clusters, IAU Symposium. 207: 207. arXiv:astro-ph/0109052. Bibcode:2002IAUS..207..745G.
  9. ^ Clark, J. S.; Negueruela, I.; Crowther, P. A.; Goodwin, S. P.; et al. (2005). "On the massive stellar population of the super star cluster Westerlund 1". Astronomy & Astrophysics. 434 (3): 949–969. arXiv:astro-ph/0504342. Bibcode:2005A&A...434..949C. doi:10.1051/0004-6361:20042413. S2CID 119042919.
  10. ^ Muno, Michael P.; Clark, J. Simon; Crowther, Paul A.; Dougherty, Sean M.; De Grijs, Richard; Law, Casey; McMillan, Stephen L. W.; Morris, Mark R.; Negueruela, Ignacio; Pooley, David; Portegies Zwart, Simon; Yusef-Zadeh, Farhad; et al. (2006). "A Neutron Star with a Massive Progenitor in Westerlund 1". Astrophysical Journal Letters. 636 (1): L41. arXiv:astro-ph/0509408. Bibcode:2006ApJ...636L..41M. doi:10.1086/499776. S2CID 10349450.