September 27, 2011

Stellar, II

The computers at work. Harvard-Smithsonian photo.

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.

Henrietta Swan Leavitt

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.

At the far left of the photograph is Margaret Harwood (AB Radcliffe 1907, MA University of California 1916), who had just completed her first year as Astronomical Fellow at the Maria Mitchell Observatory. She was later appointed director there, the first woman to be appointed director of an independent observatory. Beside her in the back row is Mollie O'Reilly, a computer from 1906 to 1918. Next to Pickering is Edith Gill, a computer since 1989. Then comes Annie Jump Cannon (BA Wellesley 1884), who at that time was about halfway through classifying stellar spectra for the Henry Draper Catalogue. Behind Miss Cannon is Evelyn Leland, a computer from 1889 to 1925. Next is Florence Cushman, a computer since 1888. Behind Miss Cushman is Marion Whyte, who worked for Miss Cannon as a recorder from 1911 to 1913. At the far right of this row is Grace Brooks, a computer from 1906 to 1920. Ahead of Miss Harwood in the front row is Arville Walker (AB Radcliffe 1906), who served as assistant from 1906 until 1922. From 1922 until 1957 she held the position of secretary to Harlow Shapley, who succeeded Pickering as Director. The next woman may be Johanna Mackie, an assistant from 1903 to 1920. She received a gold medal from the American Association of Variable Star Observers (AAVSO) for discovering the first nova in the constellation of Lyra. In front of Pickering is Alta Carpenter, a computer from 1906 to 1920. Next is Mabel Gill, a computer since 1892. And finally, Ida Woods (BA Wellesley 1893), who joined the corps of women computers just after graduation. In 1920 she received the first AAVSO nova medal; by 1927, she had seven bars on it for her discoveries of novae on photographs of the Milky Way.



  1. The wonders of galactic exploration can be sampled annually at the Jet Propulsion Laboratory Open House in La Canada-Flintridge. This past May, we toured the Mission Control room and watched prototype Mars Rovers clattering over boulders just as they do on Mars.

    Comment by Celia Carroll — September 27, 2011 @ 7:59 am | Reply

  2. Thank you. You’ve made these women, and soon the others, a bit better known.

    Comment by Carol — September 27, 2011 @ 9:25 am | Reply

  3. someone should write a book about them or better yet make a movie! =D

    Comment by ninachat — September 29, 2011 @ 11:47 pm | Reply

  4. If taken in 1919, the photograph must have been taken very early in that year, since Pickering died February 3, 1919. There are no obvious signs of winter, so perhaps the photograph was taken in the latter part of 1918. From the ages of the various astronomers I would guess that the photograph could not have been taken much earlier than 1919 and it is indeed a nice image showing more detail than many group photographs.

    Comment by Horace Smith — January 31, 2015 @ 4:38 pm | Reply

    • good catch – the photo was taken in May of 1913. my apologies for what i assume was a typo.

      Comment by jchatoff — January 31, 2015 @ 11:10 pm | Reply

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