The age of a cluster of stars can be judged by the:

Question

Quizplus · Accepted Answer

The turnoff point on the main sequence of the Hertzsprung-Russell diagram can be used to estimate the age of a star cluster. This is because the position of the turnoff point is related to the mass of the stars in the cluster, which in turn affects their lifetimes. Younger clusters will have more massive stars still on the main sequence, while older clusters will have mostly lower mass stars that have evolved off the main sequence.

The Age of a Cluster of Stars Can Be Judged