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Harlow Shapley: Measurement of Galaxies of Vast Distances, 1945

Calculating Center

Through his study of the distribution of globular clusters in the Milky Way, Shapley calculated that our Sun, previously thought to lie near the center of the galaxy, was 50,000 light years from the center of the Milky Way. This resulted in the first realistic assessment of the size of our galaxy. (Scientists now know that this number is approximately 26,000 light years.) Shapley correctly determined the galactic center of the Milky Way to be located in the constellation of Sagittarius. He did this by mapping out a three-dimensional distribution of the globular clusters.

As a result of Shapley's work, scientists began to have a better understanding of the Milky Way, a galaxy far larger than generally believed at that time.