Harlow Shapley

Harlow Shapley (November 2, 1885 – October 20, 1972) was an American astronomer, who served as head of the Harvard College Observatory from 1921–1952, and political activist during the New Deal and Fair Deal. Shapley used Cepheid variable stars to estimate the size of the Milky Way Galaxy and the Sun's position within it. In 1953 he proposed his "liquid water belt" theory, a concept now known as a habitable zone.