Cecilia Payne-Gaposchkin (1900 – 1979) was a British-American astronomer who discovered that stars are composed mainly of hydrogen and helium. She was able to do this because of her knowledge of nuclear physics. This was a groundbreaking discovery which was contradictory to the beliefs from that time. She is our 18^th installment of Women in Nuclear History.

1. Cecilia Payne was born May 10, 1900 in Wendover, England to Emma and Edward Payne. Her father was a London barrister, historian, musician, and an Oxford fellow. When she was four years old her father died. Her mother decided to move the whole family (with her sister and brother) to London, to ensure better education.
2. Cecilia was a good student and won a scholarship to pay all her expenses at Newnham College at Cambridge University. Initially she studied botany, but switched to physics, and then astronomy. The turning point for her was an astronomy lecture by Arthur Eddington on his Africa 1919 expedition to observe the stars near a solar eclipse to test of Albert Einstein’s general theory of relativity.
3. She completed her studies, but was not awarded a degree because Cambridge did not grant degrees to women until 1948. Harlow Shapley, who was a director of the Harvard College Observatory visited the UK and encouraged Cecilia to do further studies in astronomy in the US.
4. Harvard College Observatory had a history of hiring women known as the “Harvard Computers” before 1925. Women were preferred because they were thought to be more patient and detail oriented; they also accepted lower wages than men. Some of these women achieved high prominence: Henrietta Swan Leavitt discovered period-luminosity relationship of Cepheid variables; Annie Jump Cannon was recognized for organizing star classification: O, B, A, F, G, K, and M groups, related to their luminosity and surface temperature.
5. Cecilia became the first person to earn a PhD in astronomy from Radcliffe College of Harvard University. Her thesis: “Stellar Atmospheres; A Contribution to the Observational Study of High Temperature in the Reversing Layers of Stars” was called “the most brilliant Ph.D. thesis ever written in astronomy.” She related spectral classes of stars to their measured temperatures. As a conclusion she found that hydrogen and helium were vastly more abundant in stars compared to the Earth. Unfortunately, she was discouraged to affirm her findings since it was not supported by the known science in that time. Later prof. Henry N. Russel took credit for this discovery, only citing her work.
6. Cecilia married Russian astronomer Sergei Gaposchkin in 1934 who she met in Germany. They worked together on many scientific projects and had three children together.
7. Cecilia’s only title at Harvard was a “technical assistant” to Professor Shapley. She was also teaching students but her classes were not listed in the official catalogue. In 1956, she was finally made a full professor (the first woman so recognized at Harvard) and a chair of the Astronomy Department.
8. In 1976, the American Astronomical Society awarded her the prestigious Henry Norris Russell Prize. In her acceptance lecture, she said, “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.”
9. The asteroid2039 Payne-Gaposchkin, discovered in 1974, is named after her, as well as a volcano on Venus.
10. Cecilia died at her home in Cambridge, Massachusetts, on December 7, 1979, aged 79 after long struggle with cancer. She published several scientific books and the biography about her work and life.