Question

How was the location of the galactic center first found by Harlow Shapley?

Answer 1

Harlow Shapely was the first to realize that the Milky Way Galaxy was much larger than previously believed. He was the first to correctly determine the center of our Milky Way galaxy. He discovered it to be in the constellation of Sagittarius. He did this by analyzing the locations of globular clusters, finding them to be centered around a point somewhere in the Sagittarius constellation.

Complete answer:
To understand his approach, we must first understand what a globular cluster is. A globular cluster is a densely packed spherical collection of ancient stars orbiting mostly in the extended star halos surrounding most spiral galaxies.
What Shapley did was, he estimated the distance of these far distant stars based on the brightness of the individual stars in the cluster or sometimes, the brightness of the cluster as a whole when this was not possible. With these sets of data at his disposal he estimated the distance of our galactic center from the Earth to be around 15 kiloparsecs towards the direction of the constellation Sagittarius.
The space surrounding the galactic center is considered to be one of the brightest parts of our galaxy and it is believed that this galactic center is a super massive black hole.

Note:
Later on with the advancement in science and technology, scientists used new and better sets of data and Harlow’s technique to find out that the galactic center is about 8.3 kiloparsecs or about 26000 light years away from Earth. For his contribution in the field of astronomy, Shapely was awarded the 1945 Franklin Medal in Physics.