In 1925, she became the first person to earn a Ph.D. in astronomy from Harvard for her dissertation "Stellar Atmospheres, A Contribution to the Observational Study of High Temperature in the Reversing Layers of Stars". Astronomer Otto Struve characterized it as "undoubtedly the most brilliant Ph.D. thesis ever written in astronomy". By applying the ionization theory developed by physicist Meghnad Saha she was able to accurately relate the spectral classes of stars to their actual temperatures. The thesis established that hydrogen was the overwhelming constituent of the stars.
On a tour through Europe in 1933, she met Russian-born Sergei I. Gaposchkin in Germany. She helped him get a visa to the United States and they married in March 1934, and eventually had three children.
Payne-Gaposchkin remained scientifically active throughout her life, spending her entire academic career at Harvard. For decades she held no official position there. Not until 1938 was she given the title of "astronomer". In 1956 she became the first female tenured professor at Harvard, and later its first female department chair.
According to G. Kass-Simon and Patricia Farnes, her career marked a sort of turning point at Harvard College Observatory. Under the direction of Edward Charles Pickering, the observatory had offered more opportunities in astronomy to women than other institutions, and notable achievements had been made earlier in the century by Williamina Fleming, Antonia Maury, Annie Jump Cannon, and Henrietta Leavitt. But with Payne-Gaposchkin's Ph.D., women entered the mainstream. The trail she blazed into the largely male-dominated scientific community was an inspiration to many.
- Annie J. Cannon Award in Astronomy (1934)
- Henry Norris Russell Lectureship of the American Astronomical Society (1976)
Named after her
- The reward of the young scientist is the emotional thrill of being the first person in the history of the world to see something or to understand something. Nothing can compare with that experience... The reward of the old scientist is the sense of having seen a vague sketch grow into a masterly landscape.
- —Cecilia Payne-Gaposchkin
- Physics Today 33 (1980) 64
- QJRAS 23 (1982) 450