Multiple populations in globular clusters: the possible contributions of stellar collisions

Globular clusters were thought to be simple stellar populations, but recent photometric and spectroscopic evidence suggests that the clusters' early formation history was more complicated. In particular, clusters show star‐to‐star abundance variations, and multiple sequences in their colour–magnitude diagrams. These effects seem to be restricted to globular clusters, and are not found in open clusters or the field. In this paper, we combine the …