Despite the stars in our Galaxy typically formed in stellar clusters, only a small fraction of them today is observed associated with a cluster. This led to the conclusion that stellar clusters typically disperse in 10-100 million years. Two mechanisms are thought to be responsible for the dispersion of stellar clusters. According to the model of the “residual gas expulsion”,
Massive stars are enormous chemical laboratories where heavy chemical elements are synthesized. For instance, the alpha-elements (O, Mg, Si, Ca, and Ti) are produced by nucleosynthetic processes in the interior of massive stars. Moreover, the lifetime of massive stars is much shorter than that of low mass stars: few million years for the former compared to several billion of years
