Annie Jump Cannon

Annie Jump Cannon ( December 11, 1863 – April 13, 1941) was a US astronomer.

Harvard Observatory

Annie Cannon spent most of the remainder of her life working at the Harvard Observatory. Her early studies at the observatory involved variable stars, and she spent much time on their classification. In 1911 she was named curator of photographs at Harvard Observatory.

Related Topics:
Variable star - 1911 - Photograph

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Part of her work at Harvard involved photographing specrograms of stars, then identifying each star according to its frequency spectrum. Pickering and his assistant Williamina Fleming assigned stars a letter according to how much hydrogen could be observed in their spectra. Stars classified as A had the most hydrogen, B the next most, and so on. They developed 22 types in all, but the physical significance of stars of each type was not clear.

Related Topics:
Frequency spectrum - Williamina Fleming - Stars - Hydrogen

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Cannon had noticed that stellar temperature was the main distinguishing feature among the different spectra. So she combined the previous classification systems used at the observatory into a simplified system. She reordered the previous types by temperature and eliminated most of the spectral class types because they became redundant.

Related Topics:
Temperature - Spectral class

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Working from 1915 until 1924 on what would be published as the Henry Draper Catalogue, Cannon catalogued 225,300 stars and ordered them into stellar spectra of types O, B, A, F, G, K, M. This classification inspired the mnemonic phrase "Oh, Be A Fine Girl - Kiss Me!" still taught to astronomy students today to remember that particular order. Several other variations on the mnemonic also are in use.

Related Topics:
1915 - 1924 - Henry Draper Catalogue - Stellar spectra - O, B, A, F, G, K, M - Mnemonic - Variations on the mnemonic

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Unlike previous classification systems, Cannon's system related the amount of hydrogen observed to a physical property of the stars. This system became the widely-accepted astronomical standard by 1910.

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Cannon reviewed photographic plates that contained stellar spectra, then called out each classification to an assistant, who would record the classification. Her hearing difficulty

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made it possible to focus entirely on her work, and she became

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exceptionally quick and accurate at analyzing stellar spectra.

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On average, Cannon classified three stars a minute in sparsely populated regions of the sky, and her speed was half that for denser regions of the sky.

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In 1922 she was dispatched to Harvard's observatory at

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Boyden Station, Peru for six months. At the observatory she

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photographed the stars that are only visible in the southern

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hemisphere. After her return, she began working on the

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Henry Draper Extension, which was published between 1929

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and 1949.

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In 1931, Cannon became the first woman to receive the Henry Draper Medal from the National Academy of Sciences. In her honor, the American Association of University Women presents the Annie J. Cannon Award in Astronomy each year to a woman starting her astronomical career.

Related Topics:
Henry Draper Medal - National Academy of Sciences - American Association of University Women - Annie J. Cannon Award in Astronomy

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Cannon also was a women's suffrage advocate and a member of the National Women's Party. During her lifetime, Cannon turned over most prize money she received to universities so they could use it for scholarships for young women studying astronomy.

Related Topics:
Women's suffrage - National Women's Party

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During her life's work, she also discovered over 300 variable stars, 5 novae, and a binary star. Her catalog work resulted in the classification of about 350,000 stars. She continued working at the observatory until age 76, only stopping due to heart disease. Cannon died in Cambridge, Massachusetts.

Related Topics:
Variable stars - Nova - Binary star - Cambridge, Massachusetts

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