The census-taker of the sky

...or "Oh! Be A Fine Girl — Kiss Me!"

Known as the “census taker of the sky,” Annie Jump Cannon was a brilliant astronomer who was known as a “computer” for much of her professional life. She is now credited with classifying 5,000 stars per month from 1911 to 1915 and 350,000 stars during her life.

Hired to work at the Harvard College Observatory under Edward Pickering in 1894, she worked as part of a group of women known as “computers,” whose job was to identify and catalogue stars. Under Pickering’s direction — and while earning as little as 50 cents an hour — these women classified all the stars in the sky.

Cannon developed a new system that classified stars (mainly based on temperature) which revolutionized the way scientists classify stars. Known as the Harvard spectral classification system, Cannon’s sequence — which employs the mnemonic device “Oh! Be A Fine Girl — Kiss Me!” (OBAFGKM) — is still used today. One may imagine some irony in her choice of mnemonic.

In 1922, the International Astronomical Union adopted Cannon’s method as the official spectral classification system. Cannon also worked for women’s rights. She was dedicated to fighting for women’s suffrage and was a member of the National Women’s Party. In 1923, Cannon was voted one of the twelve greatest living women in America by the National League of Women Voters.

Also in 1923, she became the first woman to receive an honorary degree from Oxford University. Toward the end of her life, and after four decades at Harvard, Cannon was appointed to a permanent faculty position in 1938. She died in April of 1941 at the age of 77 and worked at Harvard until her death.