Today is the 120th anniversary of Cecilia Payne-Gaposchkin’s birth. She took theoretical developments in the new science of quantum mechanics and used them to explain the spectra of stars and ultimately what stars are made of 1/4

Prior to Payne-Gaposchkin many astronomers had worked out that the stellar spectra (how much light of different colours a star gives off) fell in to several categories. Payne-Gaposchkin used theoretical work by Boltzmann and Saha to explain why stars had the spectra they did 2/4

Think of Annie Cannon and her contemporaries as being like Linnaeus, putting stars into categories. Payne-Gaposchkin was Franklin, Crick, Watson & Wilkins revealing why stars fell into those categories 3/4

Payne-Gaposchkin’s work also showed that the Sun and other stars were made of mostly of hydrogen and helium. Previously it was thought the Sun had a similar composition to the Earth. 4/4