The stars at the turnoff point in the H-R diagram of the Hyades star cluster have an absolute magnitude of approximately M = +2, whereas those at the turnoff point in the cluster M41 have M = 0. From this information, we can say with certainty that the Hyades cluster:
A)is farther away than M41.
B)older than M41.
C)has more stars in it than M41.
D)younger than M41.

Question

Quizplus · Accepted Answer

The turnoff point in an H-R diagram indicates the brightest, hottest, and most massive stars that have exhausted their core hydrogen fuel and are beginning to evolve off the main sequence. The higher the absolute magnitude of the stars at the turnoff point, the younger the cluster. Therefore, since the Hyades stars have a lower absolute magnitude at the turnoff point than those in cluster M41, the Hyades are older than M41. The distance and number of stars in the clusters cannot be determined from this information.

The Stars at the Turnoff Point in the H-R Diagram