Born #OTD in 1900, British-American astronomer Cecilia Payne-Gaposchkin discovered that stars are primarily made of hydrogen and helium. She made her revolutionary—and correct—conclusion about stars as a student, but it was so radical that her advisers convinced her to take it out of her thesis. . . . . . . . #space #milkyway #galaxy #cosmos #cosmology #british #astronomy #astronomer #spaceexploration #solarsystem #hydrogen #blueorigin #helium #nasagov #stars #womeninscience #herstory #leadingwomen #womenwhoscience #thisiswhatascientistlookslike #womenshistory #ceciliapaynegaposchkin #thesis