Super star cluster

A super star cluster (SSC) is a very massive young open cluster 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 the Milky Way Galaxy'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 ${\displaystyle n_{e}=10^{3}}$–${\displaystyle 10^{6}}$ cm${\displaystyle ^{-3}}$ and pressures ${\displaystyle P/}$${\displaystyle k_{b}}$${\displaystyle =10^{7}}$–${\displaystyle 10^{10}}$ K cm${\displaystyle ^{-3}}$.

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