American astronomer (1863–1941)

Annie Cannon was the daughter of a Delaware state senator and was born in Dover in that state. She was one of the first girls from Delaware to attend university, being a student at Wellesley College from 1880 to 1884. After a decade spent at home, where she became deaf through scarlet fever, she entered Radcliffe College in 1895 to study astronomy. In 1896 she was appointed to the staff of the Harvard College Observatory, as it was the practice of the observatory, under the directorship of Edward Pickering, to employ young well-educated women to do calculations. She worked there for the rest of her career, serving from 1911 to 1932 as curator of astronomical photographs. In 1938, after nearly half a century of distinguished service, she was appointed William Cranch Bond Astronomer.

One of the main programs of the observatory was the preparation of the Henry Draper Catalogue of a quarter of a million stellar spectra. Stars were originally to be classified into one of the 17 spectral types, A to Q, which were ordered alphabetically in terms of the intensity of the hydrogen absorption lines. Cannon saw that a more natural order could be achieved if some classes were omitted, others added, and the total reordered in terms of decreasing surface temperature. This produced the sequence O, B, A, F, G, K, M, R, N, and S. Cannon showed that the great majority of stars can be placed in one of the groups between O and M. Her classification scheme has since only been slightly altered.

Cannon developed a phenomenal skill in cataloging stars and at the height of her power it was claimed that she could classify three stars a minute. Her classification of over 225,000 stars, brighter than 9th or 10th magnitude, and the compilation of the Catalogue took many years. It was finally published, between 1918 and 1924, as volumes 91 to 99 of the Annals of Harvard College Observatory. She continued the work unabated, later publications including an additional 47,000 classifications in the Henry Draper Extension (Annals, vol. 100, 1925–36). Even as late as 1936 when she was over 70 she undertook the classification of 10,000 faint stars submitted to her by the Cape of Good Hope Observatory.

The American astronomer Annie Jump Cannon (1863-1941) made her most outstanding contribution to modern astronomy in the field of stellar spectral classification.

Annie Jump Cannon was born in Dover, Delaware, on December 11, 1863, the daughter of Wilson Lee Cannon and Mary Elizabeth Jump Cannon. One of the first Delaware women to enroll in college, she attended Wellesley College (class of 1884). Back at Wellesley in 1894 after a decade at home, she did graduate studies in mathematics, physics, and astronomy. In 1895, Cannon registered as a special student in astronomy at Radcliffe College, staying there two years.

The newly elected director of the Harvard College Observatory, Edward C. Pickering, had put Williamina P. Fleming in charge of hiring a staff of women assistants. Between 1885 and 1900, Fleming selected 20 assistants - including Cannon, who joined the staff in 1896 - to sort photographs of stellar spectra.

Cannon's early work dealt mostly with variable stars. Her greatest contributions remain in the field of stellar spectral classification. She discovered more than 300 variable stars on the photographic plates. A large number were detected from spectral characteristics. At Harvard the spectra of stars had been sorted into various groups, following the alphabetical order (A, B, C, and so on). Cannon created the definitive Harvard system of spectral classification. She rearranged groups, omitted some letters, added a few, and made new subdivisions. She proved that the vast majority of stars are representatives of only a few species. These few spectral types, with rare exceptions, can be arranged in a continuous series. Following five years of research (1896-1901), Cannon published in 1901 a description of 1,122 of the brighter stars.

Cannon's paramount contribution to astronomy was The Henry Draper Catalogue, named after the first man to photograph stellar spectra. In the Draper catalogue can be found spectral classifications of virtually all stars brighter than ninth or tenth magnitude, "a colossal enterprise embracing 225,300 stars" (Owen Gingerich).

She had described her classification in 1900 and, slightly modified, again in 1912. Most of the work of classifying the spectra was performed between 1911 and 1915. The first volume of the catalogue appeared in 1918, the ninth and final volume in 1924. She published about 47,000 additional classifications in the Henry Draper Extension (1925-1936) and several thousand more in the Yale Zone Catalogue and Cape Zone Catalogue. Moreover, 86,000 were printed posthumously in 1949. In 1922 Cannon's system of classification was adopted by the International Astronomical Union as the official system for the classification of stellar spectra. That same year she spent half a year at Arequipa, Peru, photographing the spectra of the southern stars.

Throughout her career, in the absence of a hearing aid, Cannon suffered from complete deafness. In discussions about the election of a woman to the National Academy of Sciences, Raymond Pearl of Johns Hopkins declared he could not vote for Cannon on the grounds she was deaf. Incidentally, the first woman astronomer was not elected to the academy until 1978.

Cannon was curator of astronomical photographs in charge of the collection of Harvard plates starting in 1911. In 1914 she was elected an honorary member of the Royal Astronomical Society. At that time women could not become regular members.

Honors bestowed upon Cannon after 1920 resulted from initiatives taken by her director, Harlow Shapley (and also by Henry Norris Russel, professor of astronomy at Princeton University), due to the lack of recognition at Harvard itself. She received four American and two foreign honorary degrees: from the University of Delaware; Wellesley, her Alma Mater; Oglethorpe University; and Mount Holyoke College and from the University of Groningen (Holland) and Oxford University (the first woman ever to be granted such distinction).

In 1931 she was awarded the Draper Medal of the National Academy of Sciences. In 1932 she was the laureate of the Ellen Richards Prize. She turned it over to the American Astronomical Society for a triennal award for distinguished contributions to astronomy by a woman of any nationality. Margaret Rossiter wrote: "Perhaps because she had never won an award from the AAS or been elected its president (she was treasurer from 1912 to 1919), she wanted more recognition for younger women." In 1938 President James Bryant Conant of Harvard University made her the William Cranch Bond Astronomer, a nonfaculty appointment. In the summer of 1940 she retired officially but continued to work actively until a few weeks before her death, on April 13, 1941, in Cambridge, Massachusetts.

Her life and work inspired other women to follow in her footsteps, to dedicate their abilities to science, and, for many, to choose a career in the field of 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.

1863–1941, American astronomer, b. Dover, Del. In 1897 she became an assistant in the Harvard College Observatory, where (1911–38) she was astronomer and curator of astronomical photographs. Recognizing that spectra of many stars had been photographed in the second half of the 19th cent., Cannon classified more than 500,000 stars, in the process publishing many papers on the subject. One of the most significant achievements in 20th-century astronomy and the basis for contemporary theoretical understanding of stellar evolution, the catalog, named after its patron Henry Draper, is still in use. In the course of her photographic work she discovered 300 variable stars, 5 novas, 1 spectroscopic binary, and many stars with bright lines or variable spectra. In 1896 she discovered SS Cygni, a “dwarf nova” that repeats its outbursts about every 60 days. She made a bibliography of variable stars that includes about 200,000 references. Each year the American Association of University Women presents the Annie J. Cannon Award for distinguished contributions to astronomy.

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