Cecilia Payne-Gaposchkin

Cecilia Payne-Gaposchkin was a British-born American astronomer and astrophysicist whose work on the cosmic makeup of the universe and the nature of variable stars was foundational to modern astrophysics. In her 1925 doctoral thesis she determined that stars are composed primarily of hydrogen and helium; her conclusion was initially rejected by leading astrophysicists, including Henry Norris Russell, because it contradicted the science of the time, which held that no significant elemental differences distinguished the Sun and Earth, and Russell himself is more often remembered for the same result, which he published independently four years later. Because she was a woman she was not eligible to receive a degree from the University of Cambridge for her studies there, and Harvard did not grant doctoral degrees to women at the time either, so she received her doctorate from Radcliffe College. In 1956 she became the first woman appointed as a professor and as a department chair at Harvard.