Question

How was the location of the Galactic Center first found by Harlow Shapley?

Answer 1

The distribution of globular clusters.

Explanation:

Harlow Shapley analysed the locations of globular clusters, finding them to be centred around a point somewhere in Sagittarius. He deduced that this was probably the location of the centre of the galaxy.

His distance estimates were based on the brightness of individual stars in the clusters where possible, or the brightness of the cluster as a whole where this was not possible. With the data at his disposal, he estimated the distance to the centre of the galaxy as approximately `15`kpc. Later studies with better data, but still using his techniques, indicate an estimated distance of `8`kpc or about `25`kly.