An astronomer observes a cluster of stars and constructs an HR diagram like Figure 11.6.What can he or she learn from the region marked "X"?
A) the distance to the cluster
B) the radius of the cluster
C) the mass of the cluster
D) the age of the cluster

Question

An astronomer observes a cluster of stars and constructs an HR diagram like Figure 11.6.What can he or she learn from the region marked "X"? 
A) the distance to the cluster 
B) the radius of the cluster 
C) the mass of the cluster 
D) the age of the cluster

Quizplus · Accepted Answer

The region marked "X" on the HR diagram represents the main sequence turnoff point, which is the point at which stars in the cluster begin to move off the main sequence and evolve into red giants. The position of the turnoff point can be used to estimate the age of the cluster. Therefore, the astronomer can learn the age of the cluster from the region marked "X".

An Astronomer Observes a Cluster of Stars and Constructs an HR