When the stars of the following open clusters are plotted on an H-R diagram, the absolute magnitude values for the turning points are approximately: Coma (2.4), h + $\chi$ (-2), M67 (4.5), and Pleiades (0.3). Which cluster is youngest?
A)Coma
B)h + $\chi$
C)M67
D)Pleiades

Question

Quizplus · Accepted Answer

The youngest star clusters have the brightest turnoff points on the H-R diagram because their most massive stars have not yet evolved off the main sequence. The h + $\chi$ cluster, with a turnoff point at an absolute magnitude of -2, indicates it has the most massive (and thus youngest) stars still on the main sequence.

When the Stars of the Following Open Clusters Are Plotted χ\chiχ

When the Stars of the Following Open Clusters Are Plotted $\chi$