The American astronomer Annie Jump Cannon (1863-1941) made her most outstanding contribution to modern astronomy in the field of stellar spectral classification.

Annie Jump Cannon was born in Dover, Delaware, on December 11, 1863, the daughter of Wilson Lee Cannon and Mary Elizabeth Jump Cannon. One of the first Delaware women to enroll in college, she attended Wellesley College (class of 1884). Back at Wellesley in 1894 after a decade at home, she did graduate studies in mathematics, physics, and astronomy. In 1895, Cannon registered as a special student in astronomy at Radcliffe College, staying there two years.

The newly elected director of the Harvard College Observatory, Edward C. Pickering, had put Williamina P. Fleming in charge of hiring a staff of women assistants. Between 1885 and 1900, Fleming selected 20 assistants--including Cannon, who joined the staff in 1896--to sort photographs of stellar spectra.

Cannon's early work dealt mostly with variable stars. Her greatest contributions remain...