Cecilia Payne-Gaposchkin(1900–1979)

Cecilia Helena Payne was born at Wendover in Buckinghamshire on the tenth of May 1900, eldest of the three children of Edward John Payne, a London barrister and Oxford historian of the Voyages of the Elizabethan Seamen to America, and Emma Pertz, a Prussian-born painter and the niece of the historian Georg Heinrich Pertz, editor of the Monumenta Germaniae Historica. Her father died when she was four. She was schooled at St Mary's School in Bourne End and at St Paul's Girls' School in Hammersmith, won a scholarship to Newnham College, Cambridge, in October 1919 in her nineteenth year, and took the Natural Sciences Tripos in 1923. She attended in December 1919 the Royal Astronomical Society lecture at Trinity College by Arthur Eddington reporting the May 1919 solar-eclipse expedition's confirmation of the Einstein theory of general relativity, and decided in the lecture-room that night, in her own later account, that astronomy was the field she would commit herself to.

Cambridge in 1923 did not award degrees to women (the university did not until 1948) and could not have offered her a doctoral place. She moved in September 1923 to the United States on the new Astronomical Fellowship at the Harvard College Observatory, the post that Harlow Shapley (Director of the Observatory from 1921 and the leading American astronomer of the period) had created for the leading European graduate astronomer of each year, and entered the Radcliffe College graduate programme as the first Astronomical Fellow. She took her PhD at Radcliffe in May 1925 in her twenty-fifth year on the thesis Stellar Atmospheres: A Contribution to the Observational Study of High Temperature in the Reversing Layers of Stars, the central thesis-result of which was the application of Meghnad Saha's 1920 ionisation theory to the observed spectra of the main-sequence stars.

The result of her thesis calculation was that the stellar atmospheres contained hydrogen and helium in proportions roughly a million times greater than every heavier element combined; the stars were not, as the consensus of solar and stellar astronomy of the 1920s had it, composed in roughly Earth-like elemental proportions, but were instead overwhelmingly hydrogen-and-helium objects with a small trace of heavier elements. The result was the foundational finding of modern stellar astrophysics. Henry Norris Russell, the leading Princeton stellar astronomer of the period and the referee on Payne's thesis, persuaded her on first reading of the manuscript to soften the central claim (he judged the hydrogen result almost certainly spurious on the strength of the existing solar-composition consensus); she added a sentence to the published thesis describing the hydrogen result as almost certainly not real. Russell published in 1929, four years after Payne's thesis, his own independent rediscovery of the same result and acknowledged Payne's prior work in a footnote; the hydrogen-stellar composition has been the foundational fact of modern astrophysics ever since.

She stayed at Harvard for the next forty-eight years to her retirement in 1973. She married the Russian-born Harvard astronomer Sergei Gaposchkin in March 1934, took his surname appending to her own, and worked with him through the next four decades on the photometry and spectroscopy of the variable stars, the central long programme of mid-twentieth-century stellar observational astronomy, including the catalogue of three million observations of three thousand individual variable stars that constitutes the foundational variable-star photometric data set. She was appointed by Harvard in March 1956 as the first female Chair of the Department of Astronomy and the first woman to be promoted to a tenured full professorship of any department at Harvard. She wrote the standard textbook Variable Stars (1938) and the autobiography An Autobiography and Other Recollections (1984, posthumous). She died at Cambridge, Massachusetts, on the seventh of December 1979 in her seventy-ninth year. The Payne-Gaposchkin name in modern astrophysics carries the weight of the 1925 Radcliffe thesis.