When Harvard astronomer Cecilia Payne submitted her 1925 doctoral thesis arguing that the Sun was made almost entirely of hydrogen, the field’s senior figure He... (opens in new tab)

In 1925, a British graduate student at Harvard named Cecilia Payne handed in a doctoral thesis that quietly upended astronomy. By comparing the spectral lines of stars against laboratory measurements of how atoms absorb light at different temperatures, she calculated that the Sun was made almost entirely of hydrogen and helium, with everything else — […]