Remember the Ladies: Annie Jump Cannon

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Annie Jump Cannon in 1922

Annie Jump Cannon in 1922

Annie Jump Cannon (December 11, 1863 – April 13, 1941) was an American astronomer whose cataloging work was instrumental in the development of contemporary stellar classification. With Edward C. Pickering, she is credited with the creation of the Harvard Classification Scheme, which was the first serious attempt to organize and classify stars based on their temperatures. She was nearly deaf throughout her career.

Professional history
In 1896, Cannon became a member of “Pickering’s Women”, the women hired by Harvard Observatory director Edward C. Pickering to complete the Henry Draper Catalogue, mapping and defining every star in the sky to photographic magnitude of about 9.

Anna Draper, the widow of wealthy physician and amateur astronomer Henry Draper, set up a fund to support the work. Men at the laboratory did the labor of operating the telescopes and taking photographs while the women examined the data, carried out astronomical calculations, and cataloged those photographs during the day.[9] Pickering made the Catalogue a long-term project to obtain the optical spectra of as many stars as possible and to index and classify stars by spectra. If making measurements was hard, the development of a reasonable classification was at least as difficult.

Not long after work began on the Draper Catalogue, a disagreement developed as to how to classify the stars. The analysis was first started by Nettie Farrar, who left a few months later to be married. This left the problem to the ideas of Henry Draper’s niece Antonia Maury (who insisted on a complex classification system) and Williamina Fleming (who was overseeing the project for Pickering, and wanted a much more simple, straightforward approach). Cannon negotiated a compromise: she started by examining the bright southern hemisphere stars. To these stars she applied a third system, a division of stars into the spectral classes O, B, A, F, G, K, M. Her scheme was based on the strength of the Balmer absorption lines. After absorption lines were understood in terms of stellar temperatures, her initial classification system was rearranged to avoid having to update star catalogues. Cannon came up with the mnemonic of “Oh Be a Fine Girl, Kiss Me” as a way to remember stellar classification. Cannon published her first catalog of stellar spectra in 1901.

Cannon and the other women at the Observatory were criticized at first for being “out of their place” and not being housewives. In fact, women could only get as high as assistants in this line of work and were only paid 25 cents an hour for seven hours a day, six days a week. Cannon dominated this field because of her “tidiness” and patience for the tedious work, and even helped the men in the observatory gain popularity. Cannon helped broker partnerships and exchanges of equipment between men in the international community and assumed an ambassador-like role outside of it. She wrote books and articles to increase astronomy’s status, and in 1933, she represented professional women at the World’s Fair in Chicago.

Cannon’s determination and hard work paid off. She classified more stars in a lifetime than anyone else, with a total of around 500,000 stars. She also discovered 300 variable stars, five novas, and one spectroscopic binary, creating a bibliography that included about 200,000 references. Cannon could classify three stars a minute just by looking at their spectral patterns and, if using a magnifying glass, could classify stars down to the ninth magnitude, around 16 times fainter than the human eye can see.

On May 9, 1922, the International Astronomical Union passed the resolution to formally adopt Cannon’s stellar classification system, and with only minor changes, it is still being used for classification today. The astronomer Cecilia Payne collaborated with Cannon and used Cannon’s data to show that the stars were composed mainly of hydrogen and helium.

Later life and death
Annie Jump Cannon’s career in astronomy lasted for more than 40 years, until her retirement in 1940. During this time, Cannon helped women gain acceptance and respect within the scientific community. Her calm and hardworking attitude and demeanor helped her gain respect throughout her lifetime and paved the path for future women astronomers.

Cannon died on April 13, 1941, in Cambridge, Massachusetts, at the age of 77. The American Astronomical Society presents the Annie Jump Cannon Award annually to female astronomers for distinguished work in astronomy.

Further Reading
On Annie Jump Cannon as a woman scientist, see the classic work by Margaret W. Rossiter, Women Scientists in America Struggles and Strategies to 1940 (1982). A biography of Cannon was written by Owen Gingerich: “Cannon, Annie Jump,” in: Dictionary of Scientific Biography (1971). At the death of Cannon, two important obituaries were published, one by the first laureate of the Annie Jump Cannon Prize in 1934, Cecilia Payne Gaposchkin, in Science (May 9, 1941), and the other by R. L. Waterfield, in Nature (June 14, 1941). Apart from recalling the scientific career of Cannon, they paid homage to her personality. (Encyclopedia.com)

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