Super star cluster

A super star cluster (SSC) is a very large region of star formation thought to be the precursor of a globular cluster.cite journal
author = Gallagher & Grebel
year = 2002
title = Extragalactic Star Clusters: Speculations on the Future
journal = Extragalactic Star Clusters, IAU Symposium
pages = 207
url = http://adsabs.harvard.edu/abs/2002IAUS..207..745G] 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)"cite journal
author = Kobulnicky & Johnson
year = 1999
title = Signatures of the Youngest Starbursts: Optically Thick Thermal Bremsstrahlung Radio Sources in Henize 2-10
journal = ApJ
pages = 154–166
volume = 527
url = http://adsabs.harvard.edu/abs/1999ApJ...527..154K
doi = 10.1086/308075] . 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.cite journal
author = Johnson
year = 2004
title = Extragalactic Ultracompact HII Regions: Probing the Birth Environments of Super Star Clusters
journal = Astronomical Society of the Pacific Conference Series
pages = 322
volume = 527
url = http://adsabs.harvard.edu/abs/2004ASPC..322..339J]

The unique characteristics of SSCs are their large electron densities $n\_e=10^3$–$10^6$ cm$^\{-3\}$ and pressures $P/$$k\_b$$=10^7$–$10^\{10\}$ K cm$^\{-3\}$.

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. [cite news | date=March 22, 2005 | title=Young and Exotic Stellar Zoo: ESO's Telescopes Uncover Super Star Cluster in the Milky Way | publisher=ESO | url=http://www.eso.org/outreach/press-rel/pr-2005/pr-08-05.html | accessdate=2007-03-20 ]

References

External links

* [http://www.sciencedaily.com/releases/2005/05/050528143304.htm Monster Super Star Cluster Discovered In Milky Way]