Annie Jump Cannon - an Astronomer Who Measured the Stars
The Early Years
Born in Dover, Delaware, on December 11, 1863, Annie Jump Cannon was the eldest daughter of state senator and prosperous ship builder, Wilson Cannon. Mr. Cannon and his second wife, Mary Jump, had Annie and two sons, Wilson Lee Cannon, Jr., and Robert Barrett Cannon. At an early age Mary taught Annie the constellations, how to identify them, and the stories behind them. The pair observed the sky from a makeshift observatory in the attic of their large house, further fueling Annie's interest in astronomy. Mrs. Cannon was the one who ultimately encouraged Annie to pursue her interest and suggested that she study math and the sciences at Wellesley College.
Her formal education began at local schools, including the Wilmington Conference Academy, from which she graduated in 1880 with the equivalent of a high school diploma. With her parent's encouragement, Miss Cannon attended Wellesley College located near Boston, one of the few colleges at the time that opened its doors to women. There she studied astronomy and physics under Sarah Francis Whiting, one of only a handful of women physicists in the United States at the time. The physics program at Wellesley had been modeled after the laboratory instruction methods of the M.I.T. physics professor Edward C. Pickering, who would later become the director of the Harvard College Observatory. When Miss Cannon took professor Whiting’s astronomy course, she learned how to observe the heavens with the school’s 4-inch Browning telescope. During Miss Cannon’s junior year, the Great Comet of 1882 appeared, and the astronomy class tracked its progress across the night sky. The comet put on quite a show, flaring for a period to be visible to the naked eye during daylight. She graduated as Valedictorian from Wellesley College in 1884 with a degree in physics.
While at Wellesley, the cold winters of Massachusetts did not agree with her and she contracted scarlet fever, which resulted in a significant hearing loss. As time progressed, her hearing continued to diminish until she was rendered nearly completely deaf. Miss Cannon acquired the ability to read lips, enabling her to comprehend the lectures and talk with others.
The opportunities in science for women were minimal at best in 1884 and what few jobs were available were taken by men. In the decade following her graduation, she filled her time with photography, tutoring students in mathematics and American History, and playing the organ for the Sunday School at the Methodist Church. In 1892 she embarked on a trip to Spain and Italy with her former Wellesley classmate Sarah Potter. On the trip, Miss Cannon took a small camera called a “Kamaret.” Her photos from the trip of the tourist destinations and the stories from her travels formed the basis of a book published in 1893 titled In the Footsteps of Columbus. The book became a souvenir in the 1893 Chicago World’s Fair for the Blair Camera Company.
The sudden death of her mother in 1893 drove her into despair. She wrote in her diary three months after her mother’s death, “Am still here in my little room, surrounded by memories.” To escape her grief and begin a new chapter in her life, she wrote to her former Wellesley professors asking about job openings. Miss Cannon was hired as a junior physics teacher, which allowed her to take graduate level astronomy courses. These courses made her proficient in spectroscopy and photography. Spectroscopy was becoming a new area of research and a practical tool in the laboratory to analyze the light emitted or absorbed by a substance, giving insight into the chemical composition of the material. In 1895, she enrolled at Radcliffe College as a "special student" so she could study under Edward Pickering, director of the Harvard College Observatory. Harvard professors worked in conjunction with Radcliffe College and would often repeat their lectures for the women at Radcliffe. Enrolling at Radcliffe also gave Cannon access to better equipment than she had at Wellesley.
Professional Work Begins
The Harvard College Observatory, under Pickering’s guidance, was working to observe and classify as many stars as possible. Astronomers at the observatory would photograph areas of the sky systematically through a telescope and spectrometer. The resulting spectrogram provided information about the temperature and the chemical composition of the star. The ambitious project was made possible by a grant from the estate of the wealthy amateur astronomer Henry Draper. In 1886, Draper's widow, Mary Draper, became interested in Pickering's research and agreed to fund it under the name Henry Draper Memorial. The objective-prism spectrograms produced by the sky surveys produced hundreds of photographic plates with small spectrograms of each of the stars. The work to classify each of the spectra was tedious and required great concentration–just the type of work Annie Jump Cannon was good at. In 1896, Pickering offered her a job as an assistant to Williamina Fleming, the observatory’s curator of astronomical photographs.
Miss Cannon had become part of a group known as "Pickering's Women," and they were called “computers.” The goal of Pickering and his computers was to complete the Henry Draper Catalogue by defining and mapping every star in the sky to a magnitude of 9, or sixteen times fainter than the human eye can see. This project, which first began in 1885, used surface temperatures as a means of classification. Pickering made the short-term project into a long-term endeavor in order to obtain optical spectra of as many stars as possible. While working at the Observatory, Miss Cannon continued her studies and received her M.A. from Wellesley in 1907.
The Harvard Computers - Origins of the Stellar Classification System
Miss Cannon was also interested in the discovery and recording of the light curves of variable stars. These types of stars have an output of light that varies with time. Their change in light output can happen in as quick as a few minutes up to several months, with the change in brightness as small as a flicker or a huge change, going from barely visible to brightened by many magnitudes, repeating the cycle over and over again. During the evenings, as weather permitted, she did what was considered men’s work. She used the 6-inch telescope in the observatory’s west wing to check on the variable stars that she was tracking. After months of careful observation, recording the date and time along with her estimate of the magnitude, she could construct a “light curve” for the variable star. The light curve showed the variation of the star’s brightness over time, tracing from maximum to minimum and then back again to maximum. From the light curve, the astronomers at the observatory could gain some insight into the nature of why the star varied in brightness. In 1903 she issued a catalog of 1,227 variable stars known at the time. Four years later she published a second catalog of variable stars with details on 2,000 stars. During the course of her work, Miss Cannon discovered 300 previously unknown variables and five exploding stars, or novae.
To increase the number of observers of variable stars, members of the Harvard College Observatory worked with amateur astronomers in the area to encourage them to take measurements of the brightness of the variable stars. From this cooperative arrangement between amateur and professional astronomers an organization was formed, named the American Association of Variable Star Observers (AAVSO). Annie Jump Cannon was one of the founding members of the organization and her name was one of the signatures on the incorporation certificate in 1918. Over the years she would encourage and guide the organization and help it flourish. The AAVSO is still a viable organization of amateur and professional astronomers with headquarters in Cambridge, Massachusetts.
Measuring and Cataloging the Stars
Miss Cannon threw herself into her work and began to classify the spectra of stars using a system devised by Fleming and another computer, Antonia C. Maury. The system was very complex, and Miss Cannon proposed a stellar classification system that was a simpler combination of the systems used by Fleming and Maury. Using the types of spectra devised by Fleming that used letters A,B,C, etc., Miss Cannon rearranged them to conform to Maury’s sequence of types I, II, III, etc., which was based on the order of descending temperatures of the stars. Miss Cannon’s system used a sequence of continuous change from the very hot white and blue stars of types O and B, which showed many helium lines in their spectra, through the middle temperature range stars of types A, F, G, and K, to the very cool type M stars. To give further detail to the classification scheme, Arabic numbers are also used. The spectra of some stars were very unusual and didn’t fit into the scheme, so they were designated as “peculiar” stars and detailed notes were prepared on these oddball stars. In 1910, Miss Cannon’s scheme was adopted as the official classification system at all observatories. On May 9, 1922, the International Astronomical Union passed a measure to formally adopt Miss Cannon's stellar classification system with a few minor changes (such as the order), and her OBAFGKM system maintains itself as the standard today. Our sun is a type “G” star, which is a rather common type of star. In astronomy classes all over the country, students memorized the mnemonic "Oh, Be A Fine Girl--Kiss Me" to help them remember the stellar sequence.
Fellow Harvard Observatory astronomer Cecilia Payne-Gaposchkin and Miss Cannon collaborated briefly to determine the composition of stars. They used the data that had been collected to determine that stars were mainly composed of helium and hydrogen. Miss Cannon was not theoretically inclined; rather, she had a talent for classification of the spectra of stars and was able to complete three stars per minute using her system. Just by looking at the spectral patterns she was able to classify stars. The astronomical photographs with which she and the computers worked were recorded on glass plates. A single plate would normally have hundreds of images, each spread out by a prism into a spectrum no more than an inch long. Miss Cannon would examine the spectra, which were often fuzzy and faint though a magnifying glass, and call out the spectral type of the star to an assistant.
From “Computer” to Astronomer
In 1911, Cannon succeeded Miss Fleming as the curator of astronomical photographs at Harvard University Observatory with a salary of twelve hundred dollars a year. As curator of the astronomical plates, she continued the work on what would end up being one of the greatest compilations of astronomical information by one person, the Henry Draper Catalogue of Stellar Spectra. The work was published by Harvard College Observatory in its Annals in 1890 and updated between the years 1918 and 1924. The catalogue lists the spectral types of 225,3000 stars, all of which are brighter than ninth magnitude–about the brightness of stars seen through a good pair of binoculars. The catalogue also gives the position of the stars, visual and photographic magnitudes, along with notes on any peculiarities of a specific star. After the catalogue was complete, Miss Cannon continued her work with an extension published in 1925. This extension classified fainter stars in certain regions of the sky, especially in the constellations of rich Milky Way regions in Cygnus, Sagittarius, Carina, and the Large Magellanic Cloud.
After Miss Cannon’s death in 1941, her long-time assistant, Margaret Mayall, continued with her unfinished work compiling The Henry Draper Extension. It was published in 1949 in the Harvard Annals and titled The Annie J. Cannon Memorial Volume of the Henry Draper Extension. The work was based on Cannon’s spectral classifications, though Mayall contributed the supplemental classifications.
After the death of Pickering in 1919, Dr. Harlow Shapley was appointed as the director of the Harvard College Observatory. Shapley was a Missourian and had worked as a newspaper reporter before completing his Ph.D. in Astronomy at Princeton University under the renowned astronomer Henry Norris Russell. Shapley continued the work began by Pickering, worked well with Cannon, and grew to respect her greatly. In one anecdote from Shapley’s autobiography, he recalls an example of Cannon’s phenomenal memory: “ ‘Well,’ I said, ‘any way I’d like to see the spectrum of SW Andromeda.’ (That was a faint variable-star spectrum that I had a hunch about.) She called to her assistant: ‘Will you get plate I37311?’ She just sang out that five-figure number. The girl went to the stacks and got the plate and SW Andromeda was on it!’ ”
In 1938, Cannon became the William Cranch Bond Professor of Astronomy, a title given to astronomers at Harvard who have special recognition in their field. This was the first and only award of recognition to be bestowed upon her from Harvard University. It came towards the end of her career and just three year before her death.
Awards and Honors
The Nova Medal was given to Miss Cannon by the American Association of Variable Star Observers (AAVSO) in 1922. Years later, in 1925, Cannon set another one of her "firsts" when she was awarded an honorary doctorate from the University of Oxford, the first woman to receive such an honor. During her career she would receive four more honorary doctorate degrees. This was followed by the Henry Draper Gold Medal of the National Academy of Sciences in 1931. During the award ceremony, Harlow Shapley, the presenter, spoke fondly of Miss Cannon, stating: “The benign presence of the Brick Building, noted collector of degrees and medals, author of nine immortal volumes, and several thousand oatmeal cookies, Virginia Reeler, bridge player, and, especially the recipient of the Draper Medal of the National Academy of Science—the first medal ever bestowed on a woman by the honorable body of fossils and one of the highest honors attainable by astronomers of any sex, race, religion, or political preference.”
Miss Cannon was also the first woman to be elected as an officer in the American Astronomical Society (AAS). During her time, the National League of Women Voters named her one of the twelve greatest living American women of all time. She even represented professional women everywhere at the 1933 World's Fair in Chicago. She was also nominated for membership in the National Academy of Sciences, but she was not elected because Raymond Pearl made an issue of her deafness.
The Association to Aid Scientific Research by Women awarded the 1932 Ellen Richards Research Prize for $1,000 to two worthy recipients, one being Annie Jump Cannon. She used the $1,000 prize money as seed money for an ongoing prize to be given out to a female astronomer of accomplishment on a bi-annual basis. Today the Annie Jump Cannon Award in Astronomy is given out annually to a woman astronomer in North America, within five years of receiving her doctorate, who has contributed notably to the field of Astronomy. The award now comes with a $1,500 prize and an expense paid opportunity to speak at the yearly AAS convention.
In 1940, the year before her death, Miss Cannon formerly retired from the Harvard Observatory. As is often the case for those dedicated to their field, she continued her work until the day she died on April 13, 1941, at Cambridge, Massachusetts. She died at age 77 having never married or bore any children. During her life and career, which lasted over four decades, Annie Jump Cannon helped women gain respect and acceptance within the scientific community. Though she was busy with her first love, astronomy, Miss Cannon was also an outspoken suffragist and aided in the women's civil rights movement. She helped a generation of women create careers of their own, despite the odds that were against them.
Her friend and colleague, Cecilia Payne-Gaposchkin, published an obituary for Miss Cannon in Science shortly after her death. Payne-Gaposchkin lamented the passing of her dear friend: “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.” While Harlow Shapley rued in his 1941 annual report: “The observatory suffered a heavy loss through the death of Miss Annie Jump Cannon. In her seventy-seventh year Miss Cannon was still engaged in classifying the spectra of stars, work in which she was a pioneer and which she had carried on for more that forty years.”
2019 Delaware Cannon Innovation Dollar Coin
In 2018 the United States Mint launched the “American Innovation $1 Coin Program.” The series honors innovation and innovators by issuing $1 coins for each of the fifty states, the District of Columbia, and the five U.S. territories. The state of Delaware Dollar was first in the series, since Delaware was the first state to ratify the U.S. Constitution in 1787, and was issued in 2019 in honor of the contributions made by Annie Jump Cannon. One side of the coin features a representation of the Statue of Liberty; this will be common for all the dollar coins issued through 2032. The other side of the coin features a silhouette of Annie Jump Cannon against the night sky, with a number of stars visible in the sky. The wording on the coin reads, “ANNIE JUMP CANNON/CLASSIFYING THE STARS/DELAWARE.” The dollar coins were made for collectors and were not issued for general circulation; therefore, they generally are not available from banks but must be purchased through the U.S. Mint, coin shops, or on-line retailers.
The coin will become an immortal tribute to a woman who broke barriers and made a lasting contribution to all mankind.
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Carey, Charles W. Jr. American Scientists. Facts on File, Inc. 2006.
James, Edward T. (Editor) Dictionary of American Biography, Supplement Three 1941-1945. Charles Scribner’s Sons. 1973.
Johnson, George. Miss Leavitt’s Stars: The Untold Story of the Woman Who Discovered How to Measure the Universe. Atlas Books. 2005.
Payne-Gaposchkin, Cecilia. “Obituary-Annie Jump Cannon” Science. May 9, 1941, Vol. 93, No. 2419, pages 443-444.
Sobel, Dava. The Glass Universe: How the Ladies of the Harvard Observatory Took the Measure of the Stars. Viking. 2016.
Shapley, Harlow. Through Rugged Ways to the Stars. Charles Scribner’s Sons. 1969.
Williams, Thomas R. and Michael Saladyga. Advancing Variable Star Astronomy: The Centennial History of the American Association of Variable Star Observers. Cambridge University Press. 2011.