What did Harlow Shapley study to gain the first strong evidence for the galactic center's direction?

Answer

Globular star clusters.

Shapley focused on globular star clusters, which are dense collections of old stars orbiting in a spherical halo outside the obscuring dusty disk, thus providing a clearer line of sight.

What did Harlow Shapley study to gain the first strong evidence for the galactic center's direction?

#Videos

How We Found Earth's Location in the Milky Way - YouTube

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