Cecilia Payne-Gaposchkin (1900–1979) 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 was foundational to modern astrophysics.
Photograph credit: Science Service; restored by Adam Cuerden
