Trumpler discovered the effect of interstellar dust by comparing two different distance measurements of distant clusters. The first was based on appearance (concentration of stars toward the center, etc.), which was unaffected by dust. The other was spectroscopic parallax (use of the H-R diagram), which was affected by dust. What should such a comparison show?
A) The H-R diagram should always give larger distances.
B) The H-R diagram should always give smaller distances.
C) There should be no difference in the distances.
D) The distances should be different, but sometimes the H-R diagram should give the larger distance and sometimes the smaller distance depending on the actual distance to the cluster.

Question

Quizplus · Accepted Answer

The H-R diagram method would give larger distances because interstellar dust dims the light from stars, making them appear fainter and thus seemingly further away than they actually are when using spectroscopic parallax.

Trumpler Discovered the Effect of Interstellar Dust by Comparing Two