Which type of cluster is typically older, exhibiting more stars that have reached the end of their life cycle?

Globular clusters are typically older and contain a higher proportion of stars that have reached the end of their life cycles compared to other types of clusters. These clusters are characterized by their tightly bound spherical formations and contain thousands to millions of stars. The stars within globular clusters are generally older populations, often comprising mainly older main-sequence stars, red giants, and white dwarfs.

The age of globular clusters means that many of their stars have undergone significant stages of stellar evolution, resulting in a lack of new, massive stars. This evolutionary state gives globular clusters a distinct population of stars that can offer valuable insights into the history of star formation in the universe.

In contrast, open clusters contain younger stars, often still in their main-sequence phase, along with ongoing star formation. Star-forming clusters and protostar clusters, as suggested by their names, indicate regions where new stars are actively forming and are generally composed of younger stars, which have not yet exhausted their hydrogen fuel. Thus, globular clusters stand out as the best answer when considering clusters that are older and filled with stars at the later stages of their life cycles.