Cecilia Payne-Gaposchkin

Cecilia Payne-Gaposchkin (born Cecilia Helena Payne; – ) was a British-born American astronomer and astrophysicist. In her 1925 doctoral thesis she proposed that stars were composed primarily of hydrogen and helium. Her groundbreaking conclusion was initially rejected, because it contradicted the science of the time, which held that no significant elemental differences distinguished the Sun and Earth. Independent observations eventually proved that she was correct. Her work on the nature of variable stars was foundational to modern astrophysics. Provided by Wikipedia