What useful purpose did RR Lyrae stars serve for Harlow Shapley in locating the galactic center?
A) Their brightness variations allowed accurate distances to be measured.
B) They emit copious amounts of infrared radiation and are thus visible through interstellar dust,which obscured visible light.
C) They are concentrated in the galactic center and so defined its direction.
D) They are important spiral arm tracers and thus defined the shape of the Galaxy.

Question

Quizplus · Accepted Answer

RR Lyrae stars are standard candles, which means their period-luminosity relationship can be used to determine their distance accurately. By measuring the distance to a large sample of RR Lyrae stars in different directions from Earth, Harlow Shapley was able to map out the distribution of stars in the Milky Way and locate the position of the galactic center.

What Useful Purpose Did RR Lyrae Stars Serve for Harlow