When Williamina Fleming started working for Edward Pickering at the Harvard College Observatory in 1881, she did mostly clerical work and mathematical calculations. But when Mary Anne Draper, widow of amateur astronomer Henry Draper, gave Pickering the money for a catalogue of stellar spectra to be named in Henry’s honor, Fleming was put in charge of the first serious attempt to classify the stars.
By the time the Draper Catalogue of Stellar Spectra was published in 1890, Fleming had done most of the classification of the 10,000-plus stars listed.
In 1897, Pickering and Antonia Maury – his niece and another of his female ‘computers’ – published a more detailed study and in 1901, Pickering and Annie Jump Cannon published a study of bright stars in the Southern Hemisphere. As work on the final Henry Draper Catalogue got under way, the women of Pickering’s staff were cataloguing 5,000 spectra a month.
We don’t know anything about many of these women and not very much about even the best known. Fleming – famously ‘the maid’ Pickering hired to replace an incompetent male assistant – was apparently a gifted manager as well as mathematician, but she seems to have been the only one without a college degree.
The women at the Observatory were from Wellesley, Radcliffe and Vassar, some with advanced degrees. They had been born into a world that was gradually allowing them to study, but which had yet to open doors to put their learning to use. Pickering’s Observatory was a rare opportunity for these women astronomers to practice their craft and – despite having to live with the ignominious label of being part of ‘Pickering’s Harem’ – practice it they did.
Chief among them is probably Henrietta Swan Leavitt (1868 – 1921), whose scientific accomplishments led her to be considered for a Nobel Prize, an honor prevented by her untimely death.
In 1893, Leavitt began as a computer, studying photographic plates and measuring and cataloguing their brightness. Eventually she discovered a pattern in the stars of the Magellanic Cloud, a relationship between luminosity and periodicity. By 1908, she was ready to publish preliminary results and in 1912 she confirmed them – there was a predictable relationship between the brightness of these stars and their pulsation.
Leavitt had discovered the Cepheid variables and thus a way to measure stellar distances. It was her work that Edwin Hubble used to form the theory of the expanding universe. The Cepheid variables changed the way mankind understood the universe.
(In 1920 the Great Debate of astronomy was held, the topic being, Are the Milky Way and the Universe synonymous? In 1924, Hubble used the Cepheid variables to prove the existence of galaxies outside the Milky Way.)
We will get back to Annie Jump Cannon at a future date – she is the only one of the big names (Fleming, Maury, Cannon, Leavitt) to appear in the photo below, taken in 1919. But some good soul at Harvard identified all of the women shown and so will I. Margaret Harwood, btw, provides a link to one of great American women of science and we will definitely get back to her too.