Annie Jump Cannon - Professional History

Professional History

In 1896 Cannon became a member of Pickering’s women, the women hired by Harvard Observatory director Edward Charles Pickering to complete the Draper Catalog mapping and defining all the stars in the sky to photographic magnitude of about 9.

Anna Draper, the widow of Henry Draper, who was a wealthy physician and amateur astronomer, set up a fund to support the work. Pickering made the Henry Draper Catalog a long-term project to obtain the optical spectra of as many stars as possible, and also to index and classify stars by spectra. If making measurements was hard enough, the development of a reasonable classification was at least as difficult.

Not long after the work on the Draper Catalog began, a disagreement developed as to how to classify the stars. Antonia Maury, who was also Henry Draper's niece, insisted on a complex classification system while Williamina Fleming, who was overseeing the project for Pickering, 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. The mnemonic of "Oh Be A Fine Girl, Kiss Me" has developed as a way to remember stellar classification.

The female astronomers doing this groundbreaking work at Harvard Observatory earned 25 cents per hour, which was less than what the secretaries at the university earned.

Cannon’s work was “theory-laced” but simplified. Her observation of stars and stellar spectra was extraordinary. Her Henry Draper Catalogue listed nearly 230,000 stars, all the work of a single observer. Cannon also published other catalogues of variable stars, including 300 that she discovered. Her career lasted more than 40 years, during which time women gained acceptance within the scientific community.

Annie Jump Cannon died April 13, 1941 after receiving a regular Harvard appointment as the William C. Bond Astronomer. She also received the Henry Draper Medal, which only one other female has won, Martha P. Haynes (who shared it with a male colleague).