A super star cluster (SSC) is a very large region that is thought to be the precursor of a globular cluster. They typically contain a very large number of young, massive stars that ionize a surrounding H II region, similar to our Milky Way's so-called "Ultra dense H II regions (UDHIIs)". An SSC's H II region is in turn surrounded by a cocoon of dust. In many cases, the stars and the H II regions will be invisible to optical observations due to high levels of extinction. As a result, the youngest SSCs are best observed in radio and infrared.
The unique characteristics of SSCs are their large electron densities – cm and pressures – K cm.
While there are many examples of SSCs in other galaxies, Westerlund 1 may be the only cluster in the Milky Way deserving of the title.
See also 
- ^ Gallagher & Grebel (2002). "Extragalactic Star Clusters: Speculations on the Future". Extragalactic Star Clusters, IAU Symposium: 207. arXiv:astro-ph/0109052. Bibcode:2002IAUS..207..745G.
- ^ Kobulnicky & Johnson; Johnson, Kelsey E. (1999). "Signatures of the Youngest Starbursts: Optically Thick Thermal Bremsstrahlung Radio Sources in Henize 2-10". ApJ 527 (1): 154–166. arXiv:astro-ph/9907233. Bibcode:1999ApJ...527..154K. doi:10.1086/308075.
- ^ a b Johnson (2004). "Extragalactic Ultracompact HII Regions: Probing the Birth Environments of Super Star Clusters". Astronomical Society of the Pacific Conference Series 527: 322. arXiv:astro-ph/0405125. Bibcode:2004ASPC..322..339J.
- ^ "Young and Exotic Stellar Zoo: ESO's Telescopes Uncover Super Star Cluster in the Milky Way". ESO. March 22, 2005. Retrieved 2007-03-20.
- ^ Astronomy and Astrophysics, "On the massive stellar population of the super star cluster Westerlund 1", Clark, J. S.; Negueruela, I.; Crowther, P. A.; Goodwin, S. P., Volume 434, Issue 3, May II 2005, pp.949-969, doi:10.1051/0004-6361:20042413 , Bibcode: 2005A&A...434..949C , arXiv:astro-ph/0504342v2
- ^ Astrophysical Journal, "Star Formation in R136: A Cluster of O3 Stars Revealed by Hubble Space Telescope Spectroscopy", Massey, Philip; Hunter, Deidre A., 01/1998, v.493, p.180, doi:10.1086/305126 , Bibcode: 1998ApJ...493..180M
- ^ "The Star Clusters in the Starburst Irregular Galaxy NGC 1569" http://adsabs.harvard.edu/abs/2000AJ....120.2383H
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