Payne · 1925
Cecilia Payne defends her hydrogen-stellar thesis at Harvard
In the spring of 1925 the twenty-five-year-old English-born Harvard astronomy graduate student Cecilia Payne completed her PhD dissertation on the spectral analysis of stellar atmospheres, demonstrating from a quarter of a million stellar spectral lines that hydrogen and helium are not minor stellar constituents (as the prevailing post-1900 astrophysical orthodoxy held) but the overwhelmingly dominant elements of the stars and (by extension) of the visible universe. The Princeton astrophysicist Henry Norris Russell, the American stellar-astrophysics authority of the period to whom the Harvard astronomy department circulated the thesis for external review, told Payne that the hydrogen-dominance conclusion was so radical that no thesis advisor would accept it and recommended she rewrite the conclusion. She inserted into the final submitted thesis the qualifying sentence that *the enormous abundance derived for these elements in the stellar atmosphere is almost certainly not real* and took the PhD on the qualified text. Four years later, in 1929, Russell published his own paper independently confirming her result, attributed the discovery to himself, and the hydrogen-dominance finding was accepted into the literature. The 1925 thesis remains, by the consensus of modern astrophysical history, the single most consequential PhD dissertation in twentieth-century astronomy.
It is the afternoon of an unrecorded day in April 1925, in the office of the Harvard College Observatory at 60 Garden Street, Cambridge, Massachusetts, in the spring light through the eastern windows over the Cambridge Common. She is twenty-five years old. She is Cecilia Helena Payne, born at Wendover in Buckinghamshire on 10 May 1900, daughter of the English barrister Edward John Payne and the German-immigrant Emma Pertz. She had been educated at the St Paul's Girls' School in Hammersmith, had taken first-class honours in the natural-sciences tripos at Newnham College Cambridge in 1923 on the Eddington-and-Rutherford working programme of the Cambridge physics-and-astronomy department, and had emigrated to Harvard in October 1923 on the Harvard-fellowship offer that the senior Cambridge astronomer Eddington had arranged on her behalf.
On the desk in front of her is the typescript final draft of the thesis, four hundred and twenty pages, completed after the three-week working revision-cycle that the Henry Norris Russell external-review correspondence has imposed. The thesis title is Stellar Atmospheres: A Contribution to the Observational Study of High Temperature in the Reversing Layers of Stars. The substantive conclusion of the thesis is the calculation that hydrogen comprises about seventy per cent and helium about twenty-eight per cent of the mass of the stellar-atmosphere material that the Mount Wilson and Harvard spectroscopic-photographic plates of the 1922-1924 working period have catalogued.
She thinks: the hydrogen-dominance finding is the senior-novel-conclusion of the thesis. The small finding inverts the prevailing late-Victorian post-Henry-Rowland astrophysical orthodoxy that the stellar-atmosphere composition is approximately the terrestrial-rocky-planet composition.
She thinks: Russell has told me that the finding is so radical that the post-Russell external-review will not accept the thesis on the unqualified text. Russell has recommended that I insert the qualifying-sentence in the thesis conclusion that the hydrogen-dominance abundance is not real but is an artefact of the spectroscopic-temperature-calibration method.
She thinks: the qualifying-sentence is not what the data shows. The small data shows the hydrogen-dominance result. The small senior Russell-led external-review will not accept the thesis unless I insert the qualifying-sentence. I will insert the qualifying-sentence and take the PhD on the qualified text. The small hydrogen-dominance finding will be in the published literature whatever the qualifying-sentence says, and the senior post-1925 working spectroscopic-astronomical research will confirm it within the five years.
She inserts the qualifying-sentence on the page-three-hundred-and-eighty-eight conclusion-paragraph and submits the thesis to the Harvard astronomy department on 9 May 1925. She takes the PhD oral-examination on 15 May 1925 and is awarded the Radcliffe College PhD in Astronomy on 18 June 1925 (the first PhD in Astronomy from Radcliffe College, the Harvard's-women's-graduate-school affiliate, and the first PhD in Astronomy awarded to a woman at any small American university). Henry Norris Russell publishes the confirmation-paper of the hydrogen-dominance result in the Astrophysical Journal in February 1929, attributes the discovery to himself, and the hydrogen-dominance result is accepted into the post-1929 stellar-astrophysical literature on the Russell-attribution working basis. Payne herself remains at Harvard for the subsequent fifty-four years, marries the Russian-American astronomer Sergei Gaposchkin in 1934, is appointed the first woman to hold a full Harvard professorship in 1956, and serves as the Chair of the Harvard Astronomy Department from 1956 to 1960. The small Cecilia Payne 1925 thesis is now generally regarded as the single most consequential PhD dissertation in twentieth-century astronomy.