Payne entered the University of Cambridge in 1919. A lecture by astronomer Sir Arthur Eddington on his expedition to the island of Principe that confirmed Einstein’s theory of general relativity inspired her to become an astronomer. Eddington encouraged her ambition, but she felt there were more opportunities for a woman to work in astronomy in the United States than in Britain. In 1923 she received a fellowship to study at the Harvard College Observatory in Cambridge, Mass., after a correspondence with its director, Harlow Shapley.
Beginning in the 1880s, astronomers at Harvard College such as Edward Pickering, Annie Jump Cannon, Williamina Fleming, and Antonia Maury had succeeded in classifying stars according to their spectra into seven types: O, B, A, F, G, K, and M. It was believed that this sequence corresponded to the surface temperature of the stars, with O being the hottest and M the coolest. In her Ph.D. thesis (published as