What useful purpose did variable stars serve for Harlow Shapley in locating the galactic center?
A) Variable stars are important spiral arm tracers and thus defined the shape of the Milky Way Galaxy.
B) The brightness variations of variable stars allowed accurate distances to be measured.
C) Variable stars emit copious amounts of infrared radiation and are thus visible through interstellar dust that obscures visible light.
D) Variable stars are concentrated in the galactic center and so defined its direction.

Question

Quizplus · Accepted Answer

The brightness variations of variable stars, particularly Cepheid variables, allowed Harlow Shapley to measure accurate distances to globular clusters in which these stars were located. By determining the distances to these clusters around the Milky Way, Shapley was able to estimate the position of the galactic center.

What Useful Purpose Did Variable Stars Serve for Harlow Shapley