December 11 – Happy Birthday, Annie Jump Cannon

Posted on December 11, 2014

As a young adult, Annie Jump Cannon (who was born on this date in 1863) was stricken with scarlet fever. She recovered, but she had lost almost all of her hearing.

Cannon was almost entirely deaf!

Luckily for Cannon, her mother had raised her with a love of learning and had always encouraged her to follow her dreams. Cannon had taken math, chemistry, and biology courses at Wellesley College but had ended up pursuing her biggest love: astronomy. And she had graduated from Wellesley with a degree in physics...

Before her illness, Cannon had traveled from America (where she was born and raised) to Europe to photograph a solar eclipse. After recovering from her illness, Cannon asked one of her favorite professors, Sarah Frances Whiting, for help getting a job in astronomy. Whiting was able to arrange for Cannon to teach and take graduate-level courses at the college – which is probably quite tough to do when you're deaf!

At the time, almost all colleges were separated into women's colleges and all the other colleges (which enrolled only men). Cannon enrolled at Radcliffe, a women's college founded near Harvard College (today one of the best universities in the world), so she could gain access to a better telescope. Soon Harvard professor Edward C. Pickering hired Cannon as his assistant at the Harvard College Observatory. And so she became a member of “Pickering's Women,” a group of women working together with Pickering to complete a star catalog.

Cannon had already written a paper about spectroscopy, the study of visible light spread into the rainbow-colored spectrum – which is another way of saying that the light is spread out according to its wavelength. (Red light has a longer wavelength than violet light.) So when Pickering decided to obtain the optical spectra of as many stars in the catalog as possible, and to classify the stars by spectra, she was in a great position to help the group do so.

Actually, several of the women working on the classification project disagreed about how the stars should be classified. Cannon created a compromise by coming up with system that was fairly simple but complex enough to be useful, with stars divided up into spectral classes O, B, A, F, G, K, and M. She also came up with the mnemonic “Oh, Be A Fine Girl, Kiss Me!” as a way to remember the classes.

Cannon published her first catalog of stellar spectra in 1901. By 1922, the International Astronomical Union passed a resolution to adopt her classification system.

And Cannon is remembered today as having classified more stars in her lifetime than any other person, male or female. She classified around 500,000 stars! (That's half a million!) Also, she discovered 300 variable stars, five novas, and one spectroscopic binary.

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