Annie Jump Cannon

Annie Jump Cannon was an American astronomer who single-handedly classified more stellar spectra than anyone in history. Born in Dover, Delaware, she studied physics at Wellesley College and later joined the Harvard College Observatory as one of the "Harvard Computers" — a group of women hired by Edward C. Pickering to analyze astronomical data. Cannon developed the Harvard spectral classification system, organizing stars into the sequence O, B, A, F, G, K, M (remembered by the mnemonic "Oh Be A Fine Girl/Guy, Kiss Me"), based on temperature from hottest to coolest. Over her 40-year career, she personally classified over 350,000 stellar spectra for the Henry Draper Catalogue — a rate of up to 300 stars per hour, earning her the title "Census Taker of the Sky." Nearly deaf from childhood scarlet fever, she nonetheless became the first woman to receive an honorary doctorate from Oxford University (1925) and the first woman elected as an officer of the American Astronomical Society.

Created the stellar spectral classification system O-B-A-F-G-K-M, still the standard today. Personally classified over 350,000 stellar spectra for the Henry Draper Catalogue. First woman to receive an honorary doctorate from Oxford University (1925). Discovered 300 variable stars, 5 novae, and a spectroscopic binary. Her classification system revealed that stellar spectra form a continuous sequence based on surface temperature.