(WHTM) — On May 9, 1922, the International Astronomical Union adopted an “industry standard” for categorizing stars. Its creator was a Harvard “computer” named Annie Jump Cannon.
Cannon was born in Delaware in 1863. Early on, she had an interest in the stars. Her mother encouraged her in her interests. She studied science at Wellesley College, graduating (as valedictorian) with a degree in physics.
In 1896, she joined the “Harvard Computers” and “Pickering’s Women.” Hired by Edward Pickering, head of the Harvard College Observatory, they were the “Hidden Figures” of their time. Their job was to study spectrographs of stars photographed with the observatory telescope, classify, and catalog them. It was tedious, painstaking work (and still is, even with modern computers).
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At the time she started at the observatory, though, how to classify the stars was a bit of an issue. Two of the computers had created competing methodologies. The classification system devised by Williamina Fleming was based on measuring hydrogen lines in the spectrograph. Antonia Maury developed a system using helium lines. Both systems had a number of classes.
Annie Jump Cannon devised a system that combined the best elements of both. In addition she simplified the classification system, creating a system with just seven classes of stars, starting with O, the hottest, B, A, F, G, K, and M, the coolest. (In case you’re wondering, our sun is a Class G.) It was this method of spectral classification that was officially adopted by the International Astronomical Union on May 9, 1922, and is still used today.
Cannon became known for the phenomenal speed at which she could classify stars. By 1913, she was doing 200 stars an hour, or about three per minute. Over her lifetime she classified about 350,000 stars and discovered 300 variable stars and five novae. She was nicknamed the “Census taker of the sky.”
Over the years Cannon garnered many honors, including becoming the first woman to receive an honorary doctorate from Oxford University in 1925. She was also dedicated to the cause of women’s suffrage. In 1929, the National League of Women Voters listed her as one of the twelve greatest living American women. But it was not until 1938 that she officially became a member of the Harvard faculty when she was named William C. Bond Professor of Astronomy. She retired from the observatory in 1940 but kept coming in and doing research until she died in 1941.
Information in the story was sourced from: Wikipedia, Saturday Evening Post, Britannica.com, Projectcontinua, sdsc.edu, massivesci.com, womenshistory.org, amphilsoc.org, wowstem.org, and St. Andrews UK.