Harlow Shapley (1885-1972), American astronomer sitting at a desk. Shapley is best known for determining the size and shape of our galaxy, the Milky Way. Shapley graduated from the University of Missouri with an astronomy degree in 1911, and gained his PhD from Princeton two years later. His major work was on Cepheid variables; stars which vary in brightness with a period related to their luminosity. He studied the distribution of these stars in globular clusters (huge spherical star clusters). From this, he determined that the Milky Way was disc-shaped, that globular clusters were distributed around its centre both above and below the disc, and that the Sun was a considerable distance from the centre. He later served as the director of the Harvard College Observatory from 1921 to 1952.