The young female astronomer who worked out what the sun is made of
By 
Mike Sutton2025-06-23T08:39:00
100 years ago, Cecilia Payne deduced that the sun is mainly made of hydrogen – but was encouraged to downplay her findings by her PhD supervisor. Mike Sutton takes up the story
Although the spectra of many elements had been detected in starlight, their relative proportions could not yet be measured. Then in 1915, a Harvard PhD candidate discovered that stars are mainly composed of hydrogen. But Cecilia Payne’s figures differed so radically from the existing professional consensus that her supervisor – fearing the examiners might reject her thesis – advised adding a disclaimer. To secure her doctorate she complied, though further research soon confirmed her original conclusions.