Annie Jump Cannon, Census Taker of the Sky

Annie Jump Cannon, 11" x 14" linocut by Ele Willoughby, 2024

I knew the #PrinterSolstice prompt "spectrum" called for another scientist portrait!

My hand printed lino block portrait of trailblazing American astronomer Annie Jump Cannon (December 11, 1863 – April 13, 1941) shows her with her stellar classification system which sorted stars based on spectral types and turned out to reveal their temperature from hot blue stars through cool red stars into O,B,A, F, G, K and M, as shown on the Hertzsprung-Russell diagram behind her. Along with her supervisor Edward C. Pickering, she is credited with the creation of the Harvard Classification Scheme, the first serious stellar classification scheme. The name, citing Harvard rather than Cannon herself, who still lacked a university appointment, makes her achievement less visible than it might have been.

The eldest of three daughters of Delaware shipbuilder and state senator Wilson Cannon and his second wife Mary Jump, Annie was born in Dover, Delaware. Her mother taught her the constellations, home economics (and the organization skills she would later need) and encouraged her to pursue her own interests. Annie and her mother used old astronomy textbooks to identify stars they could see by climbing out a trapdoor onto their roof. She studied mathematics, chemistry, and biology at Wellesley College, a top school for women, where she excelled at math. She studied physics with Sarah Frances Whiting, one of the few US women physicists at the time, and became the valedictorian. She graduated with a degree in physics in 1884 and returned home to Delaware. Over the next decade she studied the new art of photography, photographing her travels through Europe with her Blair box camera. The Blair company published her photos and prose about Spain, "In the Footsteps of Columbus" and distributed it as a souvenir at the Chicago World's Columbian Exposition of 1893.

A cheerful and energetic person, she lost most of her hearing as a young adult, possibly due to scarlet fever. She found it made it hard to socialize. Then her mother died in 1894, which made family life difficult too. She wrote Sarah Frances Whiting seeking a job and was hired as a junior physics teacher, which allowed her to take graduate physics and astronomy classes and study spectroscopy on her own. She gained access to a better telescope by enrolling in Radcliffe College (a women's college affiliated with Harvard) in 1894 as a "special student" which allowed her to use the he Harvard College Observatory. Harvard astronomer Edward C. Pickering hired her as his assistant in 1896. He was running a program to map and catalogue every visible star in the sky to a photographic magnitude of about 9 (16 times fainter than visible by human eye alone) to complete the Henry Draper Catalogue, a research program fund by the widow of a wealthy physician and amateur astronomer. He hired men to do the physical jobs of operating heavy telescopes and making photographs. He hired and supervised a group of women (whom he could pay as little as 25 cents an hour to work seven hours a day, six days a week) known as the Harvard Computers to do examine data, do calculations and catalogue photos - work he did not deem proper scientific analysis. Though hired as mere "computers" this team included such astronomy luminaries as Cannon, Henrietta Swan Leavitt, Williamina Fleming and Antonia Maury who made important advancements in the field. Pickering wanted the optical spectra of as many spectra as possible with the goal of indexing and classifying stars by spectra. The Draper Catalogue became an indispensable tool for astronomers.

Cannon worked at the Observatory until 1940. In her first three years, she classified 1000 stars. By 1911 she was made the Curator of Astronomical Photographs at Harvard and by 1913 she had learned to accurately classify 200 stars an hour! She published her first star catalogue in 1901. She finished her studies at Wellesley and was awarded a master's in 1907. In 1927, Pickering  said "Miss Cannon is the only person in the world—man or woman—who can do this work so quickly," about her skills in star classification.

The classification work was begun by Nettie Farrar, but she left the Observatory after a few months to get married. Antonia Maury (the first person to detect an calculate the orbit of a spectroscopic binary, and Draper's niece) took over. She insisted on a complex scheme, to the dismay of project manager Williamina Fleming (who catalogues ten thousand stars, 59 gaseous nebulae, over 310 variable stars, 10 novae and other astronomical phenomena including discovering the Horsehead Nebula) who wanted a simpler scheme. Cannon negotiated a compromise, applying a scheme dividing of stars into the spectral classes O, B, A, F, G, K, M, based on the Balmer absorption lines of hydrogen. Later when the scheme was understood to reflect stellar temperatures her initial sequence of the classes was reordered to go from hot to cold.

Cannon excelled at the work thanks to her organizational skills and patience with the tediousness of the work. Her calm, friendly and hardworking personality lead her to a sort of ambassador-like role, brokering exchanges of equipment between male colleagues.  Nicknamed "Census Taker of the Sky,"  she catalogued an estimated  350,000 stars, more than any other person. She also discovered 300 variable stars, five novas, and one spectroscopic binary.

In 1914, she was admitted as an honorary member of the Royal Astronomical Society. Awarded an honorary doctor's degree in math and astronomy from Groningen University in 1921, she became one of the first women to receive an honorary doctorate from a European university. On May 9, 1922, the International Astronomical Union passed the resolution to formally adopt Cannon's stellar classification system. With minor changes (to include intensity as well as temperature) Annie Jump Cannon's classification system is still in use today. She got the opportunity to spend six months in Arequipa, Peru, photographing stars in the Southern hemisphere. In 1925 she became the first woman to receive an honorary science doctorate from Oxford and was elected to the American Philosophical Society. In 1929 she chosen as one of the "greatest living American women" by the League of Women Voters. In 1931, she was the first woman to win the Henry Draper Medal. In 1932 she won the Ellen Richards prize from the Association to Aid Scientific Research by Woman. She represented professional woman at at the World's Fair in Chicago in 1933. She became the William C. Bond Astronomer at Harvard University in 1938.

Cecilia Payne (later Payne-Gaposchkin) used Cannon's data to show that stars are mainly composed of hydrogen and helium.

Cannon retired in 1940 but kept working at the Observatory until a few weeks before she died at 77. Her work helped women gain acceptance and respect in the field. A dedicated suffragette she was also a member of the National Women’s Party. As The Woman Citizen’s noted in 1924, despite her achievements “The traffic policeman on Harvard Square does not recognize her name. The brass and parades are missing. She steps into no polished limousine at the end of the day’s session to be driven by a liveried chauffeur to a marble mansion.” But her legacy lives on in the discoveries she made, the classification system she developed, and the trail she blazed for women in astronomy. In 1935 she created the Annie J. Cannon Prize, awarded by the American Astronomical Society, for "the woman of any country, whose contributions to the science of astronomy are the most distinguished." The first recipient became the first woman full professor of astronomy at Harvard: Cecilia Payne-Gaposchkin. Like her mother before her, and her first physics professor Sarah Frances Whiting, Annie was able to mentor and promote the next generation of women astronomers. Payne-Gaposchkin wrote in Science, upon her death, “On the thirteenth of April, 1941, the world lost a great scientist and a great woman, astronomy lost a distinguished contributor and countless human beings lost a beloved friend by the death of Miss Annie J. Cannon.” Harlow Shapely, Directory of the Harvard Observatory wrote, “Her official position at the Harvard Observatory was the William Cranch Bond Astronomer and Curator of the Photographic Collection. Her unofficial position was dean of women astronomers of the world and a leading and most honored woman scientist.”

 

References

Annie Jump Cannon, wikipedia, accessed February 2024 

Christ, Marian., Annie Jump Cannon, American Philosophical Society, January 16, 2022.

Geiling,  Natasha., The Women Who Mapped the Universe and Still Couldn’t Get Any Respect, Smithsonian Magazine, September 18, 2013

Murphy, Norah M., Eyes to the Sky: Annie Jump Cannon and the Harvard Observatory, The Harvard Crimsom, May 5, 2017

Stellar classification, wikipedia, accessed February 2024