Cecilia Payne-Gaposchkin (May 10, 1900 - December 7, 1979) was an English-American astronomer and astrophysicist. Her only career option in England was to become a teacher. After meeting Harlow Shapley, the Director of the Harvard College Observatory, who had just begun a graduate program in astronomy, she left England in 1923. In 1925 proposed in her PhD thesis an explanation for the composition of stars in terms of the relative abundances of hydrogen and helium. In 1931, she became an American citizen. On a tour through Europe she met Russian-born astrophysicist Sergei I. Gaposchkin. She helped him get a visa to the US and they married in 1934. She studied stars of high luminosity in order to understand the structure of the Milky Way. Later she surveyed all the stars brighter than the tenth magnitude. She then studied variable stars, making over 1,250,000 observations with her assistants. This work later was extended to the Magellanic Clouds, adding a further 2,000,000 observations of variable stars. These data were used to determine the paths of stellar evolution. She remained scientifically active throughout her life, spending her entire academic career at Harvard. In 1956 she became the first woman to be promoted to full professor from within the faculty at Harvard's Faculty of Arts and Sciences. With her appointment to the Chair of the Department of Astronomy, she became the first woman to head a department at Harvard. She died in 1979 at the age of 79.