CECILIA PAYNE’S STELLAR ATMOSPHERES AT 100: REVISITING THE THESIS THAT TRANSFORMED ASTROPHYSICS

This paper commemorates the centenary of Cecilia Payne’s <italic>Stellar Atmospheres</italic> … (1925), a doctoral thesis that fundamentally reshaped astrophysics by establishing hydrogen as the primary constituent of stars. Payne’s application of Meghnad Saha’s ionization theory to Harvard’s spectral data overturned the prevailing assumption that stars shared the Earth’s composition. Although Henry Norris Russell initially advised caution, regarding her conclusion as “impossible”, within a few years it became the foundation of modern stellar astrophysics. By situating <italic>Stellar Atmospheres</italic> in its institutional and historical context, this paper highlights both its scientific significance and the barriers Payne faced as a woman in early twentieth-century astronomy. Her thesis remains a cornerstone of abundance studies and a lasting reminder of the obstacles that once delayed her recognition.