The brightest main- sequence star in a cluster has a temperature of 10,000 K and a luminosity about 100 times greater than the sun. What is the approximate age of the cluster?

Question

Quizplus · Accepted Answer

Using the HR diagram, we can estimate the age of a cluster by finding the turnoff point, which is the point where the most massive stars are just starting to evolve off the main sequence. Since the brightest main-sequence star in the cluster has a luminosity about 100 times greater than the sun, we can estimate that it is about 5 times more massive than the sun. Using stellar evolution models, we can estimate that a star with 5 times the mass of the sun will have a main-sequence lifetime of about 1 billion years. Therefore, the cluster must be at least 1 billion years old. Answer C is the closest estimate.

The Brightest Main- Sequence Star in a Cluster Has a Temperature