Cecilia Payne-Gaposchkin, English-American astronomer and astrophysicist (b. 1900)
Cecilia Helena Payne-Gaposchkin (née Payne; (1900-05-10)May 10, 1900 – (1979-12-07)December 7, 1979) was a British-born American astronomer and astrophysicist who proposed in her 1925 doctoral thesis that stars were composed primarily of hydrogen and helium. Her groundbreaking conclusion was initially rejected because it contradicted the scientific wisdom of the time, which held that there were no significant elemental differences between the Sun and Earth. Independent observations eventually proved she was correct. Her work on the nature of variable stars, carried out with her husband, Sergei Gaposchkin, were foundational to modern astrophysics.