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"Oh, to be a Fine Girl!"
Annie Jump Cannon and the Stars
by Pat Sherman

"Oh, to be a fine girl. Kiss me!" Did anyone actually kiss Annie Cannon when she said this? She was certainly pretty; and, everyone who met her found her lively personality charming. But she wasn't thinking about kisses. She was thinking of stars—not Hollywood stars, but the real ones in the sky.

Although most stars appear plain white to the naked eye, Annie knew that stars could be classified by their different colors. She used her exclamation as a mnemonic device, or code, for remembering the classes of stars, from the hottest blue-white "O" stars down to the coolest red "M" ones. Nobody in the world knew as much about the colors of stars as Annie Jump Cannon. In her lifetime, she would classify nearly a quarter million of them, more than any other astronomer of her generation.

Born in Dover, Delaware, in 1863, Annie first became fascinated by stars when her mother would point out the constellations on clear nights. Perhaps because she was partially deaf, Annie concentrated on her sense of vision. Sparkling lights delighted her. She often spent hours playing with glass prisms, making rainbows by candlelight.

Fortunately, Annie's parents believed that girls should have the same academic opportunities as boys, an unusual attitude in the nineteenth century. When she turned sixteen, her father encouraged her to enroll in Wellesley College, one of the country's first four-year colleges for women. There she studied physics and learned how to use a telescope. After graduating, she continued as a special student at Radcliffe and Harvard. But opportunities for women astronomers were limited.

For many years, Annie pursued her ambitions without a full-time job. Finally in 1896, she was hired as a "computer" in the Harvard Observatory. William Pickering, the director of the Observatory, preferred to employ women because they would work for twenty-five cents an hour, half the wages of men. These human "computers" analyzed photographs of stars taken through the Observatory's telescope. Some people called the women "Pickering's Harem," as if they couldn't possibly be serious scientists. The women proved their critics wrong however, as they worked tirelessly to compile a detailed catalogue of the stars that is still used by astronomers today.

Annie specialized in spectroscopy, the study of the spectrum produced by a star's light when photographed through a prism. Because color film did not exist at that time, the spectrum appeared only as a series of dark and light lines on the photographic plate. Yet these lines could reveal the star's color, temperature, age, speed at which it rotated, and rate at which it traveled through the universe. Annie possessed an almost uncanny ability to read these spectroscopic images.

"They aren't just streaks to me," she explained. "Each new spectrum is the gateway to a wonderful new world." She felt as if the stars had "almost acquired speech" and could tell her the stories of their lives through their spectra. Analyzing thousands of photographs, she classified nearly 5,000 stars a month, sometimes as many as three a minute. Nine volumes of the catalogue are based on her work alone. As her reputation grew, astronomers from all over the world came to study her methods.

Annie received many awards and honors, including the first Draper Medal given to a woman by the American Academy of Sciences. Most important though, she never lost her enthusiasm. "I am classifying, classifying..." she wrote to a friend shortly before she died in 1941. "Of course I love to do it!" Today she is remembered by the Annie Jump Cannon Award. It is presented each year by the Association of University Women to a young woman who is beginning her own career in astronomy and hopefully finding work that she too will love for a lifetime.

Sidebar:
"Oh to Be A Fine Girl. Kiss Me" is a mnemonic device, usually a phrase or code, which is used to remember something. The following is a simple list illustrating how Annie's phrase helped her remember the classification of stars according to their heat and color.

Class Temperature Star Color

     O 30,000 - 60,000° K Blue
     B 10,000 - 30,000° K Blue
     A 7,500 - 10,000° K White
     F 6,000 - 7,500° K White (yellowish)
     G 5,000 - 6,000° K Yellow (like the Sun)
     K 3,500 - 5,000° K Orange
     M 2,000 - 3,500° K Red
     K means Kelvin degrees, which is calculated by adding 273 to Celsius degrees.

Source: http://www.astrophysical.org/starclassification.php

Resources
Camp, Carole Ann. American Astronomers: Searchers and Wonderers. New Jersey: Enslow Publishers, 1996.

Johnson, George. Miss Leavitt's Stars: The Untold Story of the Woman who Discovered How to Measure the Universe. New York: W.W. Norton, 2005.

Yost, Emily. American Women of Science, New York: Frederick A. Stokes Company, 1943.

Zach, Kim K. Hidden from History: The Lives of Eight American Women Scientists. North Carolina: Avisson Press, 2002

Internet
http://www.nasa.gov/worldbook/star_worldbook.html
http://www.skyandtelescope.com/howto/basics/3305876.html?page=1&c=y
http://www.wellesley.edu/Astronomy/Annie/

Pat Sherman is a children's author whose first picture book, 'The Sun's Daughter', was published by Clarion in 2005. She currently lives in Cambridge, Massachusetts, where she teaches writing and pursues historical research..