What Useful Purpose Did Variable Stars Serve for Harlow Shapley

question 124

Multiple Choice

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.