Annie Jump Cannon

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. □

Cannon, Annie Jump

(b. Dover, Delaware, 11 December 1863; d. Cambridge, Massachusetts, 13 April 1941),

astronomy.

Miss Cannon’s father, Wilson Lee Cannon, was a man of wide influence who became state senator in Delaware; her mother was Mary Elizabeth Jump Cannon. When Miss Cannon entered Wellesley College in the class of 1884, she became one of the first girls of her native state to go away to college. In 1894 she returned to Wellesley for graduate study in mathematics, physics, and astronomy. The following year she enrolled as a special student in astronomy at Radcliffe College, probably at the suggestion of Edward C. Pickering, who had already employed several talented women astronomers at Harvard College Observatory. Miss Cannon joined the staff at Harvard in 1896 and worked there for the rest of her life.

Miss Cannon quickly recognized the immense opportunity offered by the study of astronomical photographs, an endeavor in which Harvard Observatory had taken a foremost position under Pickering’s aggressive leadership. Much of her early work dealt with variable stars, but her greatest contributions were in the field of stellar spectral classification. On the photographic plates she discovered more than 300 variable stars, and a large number of these were detected from their spectral characteristics.

In the early work at Harvard, the spectra of stars had been sorted into various groups designated by the letters A, B, C, and so on. Miss Cannon developed the definitive Harvard system of spectral classification by rearranging these groups, omitting some letters, adding a few, and further subdividing the others. Her work proved that the vast majority of stars are representatives of but a few species; and she also demonstrated that these few spectral types, with rather rare exceptions, could be arranged in a continuous series.

In 1901, after five years of research, Miss Cannon published a description of the spectra of 1,122 of the brighter stars, a volume that proved to be the cornerstone on which her larger catalogs were based. The Henry Draper Catalogue, published as volumes 91–99 of the Annals of Harvard College Observatory, is Miss Cannon’s outstanding contribution to astronomy; it contains spectral classifications of virtually all stars brighter than ninth or tenth magnitude—a colossal enterprise embracing 225,300 stars.

Although Miss Cannon began classifying spectra in her first year at the observatory, the classifications for The Henry Draper Catalogue were made in the relatively brief interval from 1911 to 1915; but because checking and arranging the material for publication required several additional years, the final volume was not issued until 1924. Unsated, she continued her work, publishing about 47,000 additional classifications in the Henry Draper Extension (Annals, 100 [1925–1936]) and several thousand more in the Yale Zone Catalogue and Cape Zone Catalogue; another 86,000 were published posthumously in the Annals (112 [1949]).

Miss Cannon’s ability to classify stellar spectra from low-dispersion objective prism plates was quite phenomenal: her rate of more than three stars a minute and her ability to duplicate the classifications later also attest to her unusual skill and determination. While she came to recognize at a glance the characteristics that placed a star in the general sequence, she rarely failed to note the peculiarities in the spectrum. Cecilia Payne-Gaposchkin has remarked that “Miss Cannon was not given to theorizing; it is probable that she never published a controversial word or a speculative thought. That was the strength of her scientific work—her classification was dispassionate and unbiased.”

From 1911 Miss Cannon was curator of astronomical photographs in charge of the ever-growing collection of Harvard plates. In 1938 she became the William Cranch Bond Astronomer, one of the first women to receive an appointment from the Harvard Corporation. Her personal charm and cheerful excitement conveyed a spirit of enthusiasm and evoked the admiration of all who knew her, and she became universally recognized as the dean of women astronomers. Throughout her career she was almost completely deaf unless assisted by a hearing aid, a handicap that must have contributed to her immense powers of concentration.

Among her numerous honorary degrees was the first honorary doctorate awarded to a woman by Oxford University. She was for a while the only woman member of the Royal Astronomical Society—an honorary member, because women were not then admitted to regular membership. She was one of the few women ever elected to the American Philosophical Society. In 1931 the National Academy of Sciences awarded her the Draper Gold Medal, and in 1932 she received the Ellen Richards Research Prize, which—with characteristic generosit—she turned over to the American Astronomical Society to establish the Annie Jump Cannon Prize for women astronomers.

BIBLIOGRAPHY

For the most part Miss Cannon’s publications appeared in the Annals of Harvard College Observatory (note references in text). Her daily work is recorded in 201 record books preserved at Harvard College Observatory.

On Miss Cannon or her work, see Leon Campbell, “Annie Jump Cannon,” in Popular Astronomy, 49 (1941) 345–347; Owen Gingerich, “Laboratory Exercises in Astronomy—Spectral Classification,” in Sky and Telescope28 (1964), 80–82; and Cecilia H. Payne-Gaposchkin, “Miss Cannon and Stellar Spectroscopy,” in The Telescope, 8 (1941), 62–63.

Owen Gingerich

Cannon, Annie Jump (1863-1941)

American astronomer

Annie Jump Cannon developed a stellar classification system that is considered by many astronomers to be the foundation of stellar spectroscopy . The science of stellar spectroscopy analyzes the photographic spectrum of a star. The spectrum, a series of colors that can range from violet to red depending on the star's temperature , is produced by using a telescope to collect a star's light and to pass it through a spectroscope. The same effect occurs when sunlight passes through raindrops to produce a rainbow . The spectroscope also produces a series of narrow dark lines within the spectrum known as spectral lines. These lines give further clues to a star's temperature as well as composition, motion, and other information. Because the position of the spectral lines on the spectrum may vary greatly from one star to another, scientists sometimes refer to this spectrographic data as the fingerprint of a star and consider this information crucial to all stellar theories.

In devising her classification system, Cannon recognized the atmospheric temperature of a star as the most important of the various factors that determine the intensity of a star's spectral lines. Her method classified stars from hottest to coolest using capital letters to designate each major type of star. The letters O, B, A, F, G, K, and M represent the seven major categories. Cannon identified further distinctions within a major category by placing a number from zero to nine after each letter. For example, the Sun is a G–2 star.

Born in Dover, Delaware, Annie Jump Cannon was encouraged by her mother in the study of astronomy from an early age. Later, under the tutelage of two American astronomers, Wellesley professor Sarah Frances Whiting (1846–1927) and the Harvard College Observatory director Edward C. Pickering (1846–1919), Cannon became an expert in the relatively new field of astronomical spectroscopy.

It was Pickering who hired Cannon, along with a number of other women astronomers, to collect and catalog spectrographic data about the stars. Before attempting this enormous project, the astronomers needed a system by which hundreds of thousands of stars could be easily classified. Prior to Cannon's arrival at Harvard two other American astronomers, Wilamina Fleming (1857–1911) and Antonia Maury (1866–1952), had joined Pickering in devising two different classification systems. However, Pickering deemed both systems to be too complex or theoretical. Cannon borrowed from these earlier attempts in developing her own unique system of classification. Using her system, Cannon and her colleagues were able to classify the spectrum of over 300,000 stars. This information was published in the Henry Draper Catalog (1918–1924) and its extension (1925–1936). The catalog is considered to be a standard for stellar spectroscopy.

Cannon's 43-year career did not go unrewarded. In addition to receiving credit for the Draper catalogs, she also received recognition for discovering over 300 variable stars (which she incorporated into a catalog) and five novae. Cannon was the first woman to receive a doctor of astronomy degree from Groningen University (1921) and an honorary doctorate from Oxford University (1925). She was also the first woman to hold an office in the American Astronomical Society and to receive the Draper Award from the National Academy of Sciences (1931).

Scientists have used the work of Cannon and her successors to derive such information about stars as their motion, composition, brightness, and temperature. In turn, this information has led to theories about stellar life cycles. Modern astronomers, equipped with superior spectroscopes and computers have improved upon Cannon's work and are now able to sort stars into several hundred spectrographic categories. Evolving theories based upon such data are the legacy of Annie Jump Cannon's pioneering work in astronomy.

See also Stellar life cycle

Annie Jump Cannon

1863-1941

American Astronomer

Annie Jump Cannon was the first astronomer to develop a simple spectral classification system. She classified 400,000 stars—more than anyone else had achieved previously—and discovered 300 variable stars, five novas, and a double star. Cannon was the most famous female astronomer of her lifetime and was called the "Census Taker of the Sky." Cannon's successes inspired other women to pursue astronomical investigations, despite gender biases demonstrated by many male astronomers.

Born on December 11, 1863, in Dover, Delaware, Cannon was the daughter of Wilson Lee and Mary Elizabeth Cannon. Her father served in the state senate. Cannon's mother transformed their attic into an observatory for Cannon to stargaze. At Wellesley College, Cannon studied with astronomer Sarah F. Whiting (1846-1927), who taught her new research methods. After graduating in 1884, Cannon returned home, where she focused on social activities, and traveled, photographing a solar eclipse in Spain in 1892.

After her mother's sudden death, Cannon dealt with her grief by resuming her astronomical observations. She began postgraduate studies at Wellesley in 1894, assisting Whiting in the physics laboratory. Cannon also studied astronomy at Radcliffe College with Edward C. Pickering (1846-1919), director of the Harvard Observatory. He encouraged female astronomers and hired Cannon in 1896 for a position at the observatory. She examined photographic plates after her classes and observed with telescopes at night. Initially, Cannon classified 5,000 stars monthly; eventually, she was able to analyze 300 stars per hour.

Cannon's most significant achievement was improving the stellar classification system that astronomers used to survey the universe. Previous astronomers had realized that when starlight is photographed refracting through prisms, it creates a spectrum. Researchers studied spectral patterns to identify star characteristics. Early classification systems arranged spectra alphabetically from A to Q, based on composition, or by Roman numeral designations, used to indicate stars' temperatures. Pickering asked Cannon to develop a better method to record star information. She determined that the elements that compose stars create different radiant wavelengths, which form various colors in spectra. By 1901 Cannon had outlined ten star categories, based on color and brightness, that were designated by letters (O,B,A,F,G,K,M,R,N,S). The first three stars were hot white or bluish, F and G were yellow, K was orange, and the final four categories were cooler red stars. Arabic numerals were used to identify subdivisions. Cannon classified the few spectra that did not fit into this system as "peculiar" and described them in detail. The International Solar Union adopted Cannon's classification system for use in observatories worldwide. Astronomers flocked to Harvard to learn her methodology. Although other classification systems were later developed, Cannon's techniques formed their framework.

Cannon also photographed and described variable stars, compiling an extensive database for other astronomers. She served as curator of the Henry Draper Memorial Collection and, during this work, compiled more astronomical data than had any other individual. She made sure that both the northern and southern hemispheres had been completely photographed, insisting that even the faintest stars be included. Ten volumes and two supplementary editions of her work were ultimately issued, listing each star with a number and description, including its position in the sky, its brightness, its visual and photographic magnitudes, and comments on any peculiarities. Because Cannon was the sole classifier, her observations and information were consistent. This central repository helped transform astronomy from a hobby into a scientific profession with a theoretical basis.

In 1931 the National Academy of Science awarded Cannon the first Henry Draper Gold Medal given to a woman. She created the American Astronomical Society's Annie Jump Cannon Prize to fund female astronomers' research. Cannon was named Harvard's William Cranch Bond Astronomer in 1938 and given the rank of professor. She died in Cambridge, Massachusetts, on April 13, 1941. Rooms at the Harvard Observatory and the Delaware State Museum as well as a memorial volume of the Draper Catalogue were dedicated to Cannon.

ELIZABETH D. SCHAFER

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