When the stars of the following open clusters are plotted on an H-R diagram, the luminosity values for the turning points are approximately (in solar luminosities): Coma (7), h + $\chi$ (600), M67 (2), and Pleiades (70). Which cluster is youngest?
A)Coma
B)h + $\chi$
C)M67
D)Pleiades

Question

Quizplus · Accepted Answer

The H-R diagram turning point luminosity is higher for younger clusters because they have more massive stars that have not yet evolved off the main sequence. h + $\chi$ with a turning point of 600 solar luminosities indicates it has the most massive (and thus youngest) stars among the options.

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

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