Annie Jump Cannon

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One of History’s Most Famous Female Astronomers

Annie Jump Cannon had a major impact on the field of astronomy, and her system for classifying stars is still used by astronomers today.

There are not many women who counted amongst the most influential astronomers of the 20th century. One of the most famous is Annie Jump Cannon, a Delaware native and Wellesley College graduate who revolutionized science’s system of stellar classification and became one of the first women to be permanently enshrined amongst the men as one of the most prominent figures in astronomy.

Early Life and Education of Annie Jump Cannon

Cannon was born in Dover, Delaware on December 11, 1863, the eldest of three daughters born to Wilson Cannon and Mary Jump. Born with a hearing disability, she was not one to be slowed down and developed an interest in traveling and photography, even while her mother fostered her interest in astronomy and taught her the constellations.

In 1880 Cannon enrolled as a student at the young Wellesley College. While she earned her degree in physics, she also spent a lot of her time studying the stars. In particular, she was encouraged by her physics instructor, Sarah Frances Whiting, to learn about spectroscopy. In spectroscopy, incoming light (like that from a star) is broken up into its component colors, like the rainbows that appear on a wall when sunlight passes through a prism. The component colors then form a pattern of lines called a spectrum. By studying the spectra of stars, astronomers can learn a great deal about them. Cannon’s education in spectroscopy at Wellesley College was to serve her well in the years ahead.

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Cannon’s System of Stellar Classification

In 1896 Cannon was hired by Edward Charles Pickering of the Harvard College Observatory. Pickering was in the practice of hiring women to go through the enormous amounts of data generated by the observatory. For this reason, they have often dubbed his “computers.” In 1911 Cannon was appointed the observatory’s curator of observational photographs.

It was Cannon’s job to look at pictures of stellar spectra and classify them according to the pattern of color lines on each. Between 1911 and 1915 it is estimated that she classified over a quarter of a million stars. In the process, she changed the way stars are classified.

Stars are classified by letters—a star whose spectrum looks a certain way might be classified as an A star, while another with a different spectrum might be a G star, etc. Cannon eliminated some classifications (thereby simplifying the system) and rearranged the remainder. In Cannon’s system, stars are arranged by size and temperature as O, B, A, F, G, K, or M stars. O stars are the biggest, brightest, and hottest stars while M stars are small and dim. This system was given the mnemonic “Oh, Be A Fine Girl, Kiss Me.” It is also more simply known as the Harvard Classification System and is the system of stellar classification still used by astronomers today.

Annie Jump Cannon’s Legacy

The significance of Cannon’s work was obvious even during her own lifetime. In 1923 she was voted one of the twelve greatest women living in America. In 1931 she became the first woman to win the Draper Award from the National Academy of Sciences (which only one other woman has won since). She received honorary degrees from a number of universities, including Oxford. In 1938 she was appointed Harvard’s William C. Bond Astronomer.

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Annie Jump Cannon died on April 13, 1941, the year after her retirement. She lived long enough to see the first several recipients of the Annie Jump Cannon Award. First given out in 1934, this award was presented by the American Association of University Women to a female astronomer within five years of the completion of her Ph.D. As of 2006 the Award has been presented by the American Astronomical Society and is only one of the ways in which Cannon’s legacy remains strong with the astronomical community.

Source:

  • Hennessey, Logan. “Annie Jump Cannon (1863-1941).” Wellesley College.
  • “Annie Jump Cannon.” The San Diego Supercomputer Center.

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