Blue globular cluster
Blue globular clusters are less than 100 million years old and are much younger than normal globular clusters , which are usually several billion years old and which were formed at the same time as their parent galaxy ; blue globular clusters, on the other hand, only formed later.
Blue globular clusters owe their name to the numerous blue main sequence stars of the spectral types O and B, which they contain due to their small age.
Blue star clusters with star numbers similar to ordinary globular clusters are the super star clusters . On average, however, blue globular clusters have fewer stars than ordinary globular clusters. a. therefore only recently regarded as an open star cluster .
A blue globular cluster, however, needs significantly more interstellar matter to form than an open star cluster. Therefore, exceptional circumstances must exist within the parent galaxy for blue globular clusters to be able to form. This explains why blue globular clusters are absent in common large galaxies such as the Milky Way or the Andromeda Nebula and instead were first discovered in the irregular galaxies of the Magellanic Clouds ; the Large Magellanic Cloud contains a fairly large population of these objects (see list). The Triangle Nebula (M 33) also contains blue globular clusters, although this seems unusual in a spiral galaxy .