How did Harlow Shapley use the period-luminosity relationship of RR Lyrae variables to determine the size of the Milky Way galaxy
A)He determined the proper motion of globular clusters in the outer disk of the galaxy.
B)He found the distances to individual variables free floating in the halo.
C)He found the distances to open clusters found throughout the disk of the galaxy.
D)He found the distances to globular clusters distributed about the center of the galaxy.

Question

Quizplus · Accepted Answer

Harlow Shapley used the period-luminosity relationship of RR Lyrae variables to determine the distance to globular clusters distributed around the center of the Milky Way galaxy. By measuring the apparent magnitude of these variable stars and comparing them to their known luminosity, he was able to calculate their distance from Earth. Using this data, he determined that the Milky Way was much larger than previously thought, with a diameter of about 100,000 light-years.

How Did Harlow Shapley Use the Period-Luminosity Relationship of RR