Written by Peggy Wargelin, Wolbach Library, 2018.

Though Henrietta Leavitt dealt with ill health and family obligations during most of her career, as well as the slow loss of her hearing beginning at age 17, she made significant scientific discoveries and contributions.

Levitt's discovery of a way to accurately measure distances on an inter-galactic scale paved the way for modern astronomy's understanding of the structure and size of the universe. The accomplishments of Edwin Hubble, the American astronomer who established that the universe is expanding, also were made possible by Leavitt's research. Hubble often said that Leavitt deserved the Nobel Prize for her work. Mathematician Gösta Mittag-Leffler, a member of the Swedish Academy of Sciences, tried to nominate her for that prize in 1924, only to learn that she had died of cancer three years earlier. **

Her early death, at the age of 53, was seen as a tragedy by her colleagues for reasons that went beyond her scientific achievements. Her colleague Solon I. Bailey wrote in her obituary that "she had the happy faculty of appreciating all that was worthy and lovable in others, and was possessed of a nature so full of sunshine that, to her, all of life became beautiful and full of meaning."

Education

After completing undergraduate work at Oberlin College in 1888, Leavitt was accepted at the Society for the Collegiate Instruction of Women in Cambridge, MA, where some professors from Harvard University taught courses to women. (This would become Radcliffe College in 1894.) She graduated in June 1892, receiving a certificate stating that, if she had been a man, she would have qualified for a B.A.

Her final year astronomy course had been taken at the Harvard Observatory. After graduating she was honored with the opportunity to work at HCO unpaid. The head of the Observatory at this time was Edward Charles Pickering, who wanted to collect as much data as possible on the stars so that others might be helped in theoretical work. He aimed to tabulate the position, color and magnitude of as many stars as possible. Delighted to have Leavitt's assistance without having to pay her, he set her to the task of studying photographic plates and recording the required data.

It was known that many stars changed in brightness over time, so another of Leavitt's tasks was to look out for such variable stars. Finally, Pickering asked Leavitt to help create a consistent standard for star magnitude by identifying and verifying new reference stars. During 1896 Leavitt wrote up a draft manuscript of her findings.

Having submitted her draft, Leavitt took a trip to Europe. The passport application gives a physical description of Miss Leavitt: Age - 28, Stature - 5 ft 8 ins, Forehead - High, Eyes - Gray, Nose - Long, Mouth - Medium, Chin - Long, Hair - Black, Complexion - Light, Face – Long (Fig. 1a). **

Upon her return from abroad, Leavitt went to Harvard to discuss her draft with Pickering. He made some suggestions on how she might make improvements to her manuscript and then Leavitt set off for Beloit, Rock, Wisconsin where her father was the Congregational Minister.**

Return to HCO

During her time at home, Leavitt taught art at Beloit College. She longed to continue her work in astronomy, but as she explained in a letter to Pickering dated 13 May 1902:

The winter after my return was occupied with unexpected cares. When, at last, I had leisure to take up the work, my eyes troubled me so seriously as to prevent my using them so closely. **

Her eyes having recovered, she asked Pickering to send her the materials that she needed to complete the manuscript she had been working on in 1896. Her letter continued:

I am more sorry than I can tell you that the work I undertook with such delight, and carried to a certain point with such keen pleasure, should be left uncompleted. I apologise most sincerely for not writing concerning the matter long ago. I am having some trouble with my hearing, worrying, a little oddly, that stargazing might make it worse. My friends say, and I recognise the truth of it, that my hearing is not nearly as good when absorbed in astronomical work. Cold weather seems to aggravate my condition. It is evident that I cannot teach astronomy in any school or college where I should have to be out with classes on cold winter nights. My aurist forbids any such exposure. Do you think it is likely that I could find employment either in an observatory or in a school where there is a mild winter climate? Is there anyone besides yourself to whom I might apply? **

Pickering replied immediately, offering her a full-time position:

For this I should be willing to pay thirty cents an hour in view of the quality of your work, although our usual price, in such cases, is twenty-five cents an hour. If it was not possible for you to relocate, I would pay your fare for a short visit to Cambridge. You could get work in order to take home to Beloit. I do not know of any observatory in a warm climate, where you could be employed on similar work and it would be difficult to furnish you with a large amount of work that you could carry on elsewhere. In any case, I should doubt if astronomy had anything to do with the condition of your hearing, unless you have been assured that this is the case by a good aurist. **

Leavitt replied:

My dear Prof. Pickering, it has proved possible for me to arrange my affairs here so that I can go to Cambridge next month and remain until the work is completed. Your very liberal offer of thirty cents an hour will enable me to do this. **

In 1903 she returned to work at HCO, continuing there, with many breaks due to family obligations and poor health, until her death in 1921 from abdominal cancer. She lived with her uncle Erasmus Darwin Leavitt, in a large villa he had built on Garden Street in Cambridge, until he died in 1916. After a short time living alone, she and her then-widowed mother roomed together in an apartment on Linnaean Street, near the Observatory.

Astronomical Glass Plate Photographs

After the HCO established a southern station in Arequipa, Peru in 1891, tens of thousands of glass plate photographs of southern stars were sent to the Harvard Observatory for analysis and storage. The brighter a star, the more photons from it reached the photosensitive chemicals on a glass plate during the plate’s exposure (the time during which it was exposed to starlight), and the larger and darker the star’s spot became. Once the star was ideally exposed, its diameter no longer changed. Sometimes to get enough exposure to see faint stars, it was necessary for brighter stars to be overexposed. As an example, see Figure 1b, in which several stars were overexposed in order to capture some faint wisps of the Orion nebula.

In order to obtain a picture of the night sky as we see it by eye, with a dark night sky and white stars, it is necessary to shine a light through the glass plate negative onto “photo paper” to make a print or “positive”, as is done with 20th century film cameras. The Harvard Computers often worked directly with the glass negatives to see fine details more easily. It was these photonegative glass plates that Leavitt worked on, measuring magnitudes and the position of stars.

For more information on Leavitt and her science, read about her work identifying variable stars, or establishing reference stars to measure the universe. 

** = citations and further information found on : O’Connor, J. J. & Robertson, E. F. (2017) Henrietta Swan Leavitt. Retrieved from http://www-history.mcs.st-andrews.ac.uk/Biographies/Leavitt.html