Annie Jump Cannon created the Harvard Classification Scheme for stellar spectral types — the OBAFGKM system still used by every astronomer in the world today. Working as one of the "Harvard Computers" (women hired by director Edward Pickering at lower pay than men), she analysed the spectra of stars captured on glass photographic plates and sorted them into categories based on their temperature and colour. She classified over 350,000 stars during her career, working with the speed and precision of a machine — 300 stars per hour, sometimes classifying 5,000 in a single day. She lost most of her hearing in her 20s, which many historians believe helped her focus on visual pattern recognition with extraordinary intensity. Her system — remember the mnemonic "Oh Be A Fine Girl Kiss Me" — became the international standard in 1922 and remains so today. Our Sun is a G-type star because she said so.
Key Contribution
Created the OBAFGKM stellar classification system — international standard since 1922, still used by every astronomer alive today. Classified 350,000+ stars by hand. Fastest and most prolific star classifier in history. Our Sun's classification as a G-type star was defined by her system.
“In these days of great trouble and unrest, it is good to have something outside our own world, to study... the stars are absolutely democratic.”
— Annie Jump Cannon
Works & Achievements
- ✦Harvard Classification Scheme — OBAFGKM (international standard, 1922)
- ✦Henry Draper Catalogue (350,000 stellar spectra)
- ✦Henry Draper Medal (1931)
- ✦Honorary doctorate, Oxford (1925 — first woman to receive one)
- ✦American Astronomical Society — Annie Jump Cannon Award named in her honor
- ✦300 stars classified per hour — most prolific stellar classifier in history