You observe a star cluster with a main-sequence turn-off point at spectral type G2 (the same spectral type as the Sun). What is the age of this star cluster?

Question

Quizplus · Accepted Answer

The spectral type G2 corresponds to a main-sequence star with a mass of approximately 1 solar mass. The turn-off point marks the end of the main-sequence phase for the most massive stars in the cluster. The turn-off point for a cluster with solar metallicity corresponds to stars with masses of about 1.1 solar masses. Using stellar evolution models, we can estimate the age of the cluster by comparing the number of stars at the turn-off point to the total number of stars in the cluster. For a turn-off point at G2, the age of the cluster is estimated to be around 10 billion years.

You Observe a Star Cluster with a Main-Sequence Turn-Off Point