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. These clusters are referred to as "super" due to the fact that they are relatively more luminous and contain more mass than other young star clusters. The SSC, however, does not have to physically be larger that other clusters of lower mass and luminosity. 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. SSCs, such as Westerlund 1 (Wd1), have been found in the Milky Way, however, most have been observed in farther regions of the universe. Specifically, SSCs have been seen to form in the interactions between galaxies and regions of high amounts of star formation with high enough pressures to satisfy the properties needed for a star cluster to form.

The typical characteristics of SSCs:

• Large electron densities $n_{e}=10^{3}$–$10^{6}$ cm$^{-3}$
• Pressures $P/$$k_{b}$$=10^{7}$–$10^{10}$ K cm$^{-3}$.
• Mass $\gtrsim$ $10^{5}$M_☉
• Radius ≈ 5 pc ≈ $10^{19}$ cm
• Age ≈ 100 Myr (Although other sources state that observed SSCs have an age of 1 Gyr)

List

Name	Galaxy	Comments	Notes	Pictures
Westerlund 1 (Wd1)	Milky Way Galaxy	First SSC discovered in the Milky Way Galaxy.		Westerlund 1
NGC 3603	Milky Way Galaxy			NGC 3603
R136	Large Magellanic Cloud (LMC)	The prototype SSC		R136 (Located in the Tarantula Nebula)
NGC 1569 A1 and A2	NGC 1569	Galaxy contains two SSCs		NGC 1569

External links

• Monster Super Star Cluster Discovered In Milky Way