Who wrote the the best astrophysics thesis ever? There must be several contenders: for precociousness, it’s hard to beat Frank Shu’s undergraduate thesis explaining why galaxies have spiral arms, and Dave Charbonneau’s “Shadows and Reflections of Extrasolar Planets” must be right up there among top doctoral theses.
A sequence of women, most of them hired as “computers”, developed the classification scheme.The first, Williamina Fleming, did most of the work for the Draper Memorial of 10,351 stars. She classified them in a scheme assigning different letters to different types… she later revised the scheme when the element helium and its lines were identified.Antonia Maury, a niece of Henry Draper, was the next… She came up with a new classification scheme, in twenty-two classes plus five orthogonal divisions…Annie Cannon (1863-1941) who “must rank among the most dedicated of astronomers of all time and certainly as one of the most illustrious from the female ranks” (Hearnshaw 1986)… updated Fleming’s original classification scheme by accounting for ionized helium lines… Miss Cannon constructed the O-B-A-F-G-K-M sequence with decimal subdivisions that is still in use… After taking part in classifying some 5000 bright stars, she started on the Henry Draper Catalogue, the successor to the Henry Draper Memorial, in 1911 and completed the classification of 225,300 stars within four years, at an average of 30 per working hour. She had assistants but must indeed have worked diligently. Her lifetime total amounts to 395,000 classifications.
That puzzle was solved after the inï¬uence of pressure had been recognized by Pannekoek, Saha had produced his equation for ionization equilibria, and Fowler and Milne had connected stellar colors with ionization differences.
The crown came with the 1925 thesis of Cecilia Payne, the first woman to obtain an astronomy PhD at Harvard, which was later called “undoubtedly the most brilliant PhD thesis ever written in astronomy” by Struve. She showed that all stars more or less share the same composition, but display different line strengths from Saha-Boltzmann sensitivities to temperature and density. Stellar spectroscopy had matured from morphology to astrophysics.