On October 15, 1890, Williamina Fleming — formerly a maid in the household of Harvard Observatory director Edward Pickering — completed the first volume of the Draper Catalogue of Stellar Spectra, which classified 10,351 stars using a system she had developed. She was thirty-three. She had been doing this work for nearly a decade, paid at a rate below what unskilled male laborers received.

Fleming was born in 1857 in Dundee, Scotland, and emigrated to Boston with her husband, who promptly left. She was working as Pickering's maid when he, frustrated with his male assistants' work, declared his maid could do the job better and hired her. She could. She taught herself stellar spectroscopy, developed the classification system used in the Draper Catalogue, discovered 10 Novae, 52 nebulae, 310 variable stars, and the Horsehead Nebula.

Pickering's decision to staff his observatory with women — who became known as the "Harvard Computers" — was driven partly by genuine recognition of their abilities and partly by economics: he could pay them 25 cents an hour, half or less what male astronomers received. The women were not permitted to operate the telescopes. They analyzed the photographic plates the telescopes produced.

Annie Jump Cannon, another of Pickering's computers, revised and expanded Fleming's classification system into the OBAFGKM system still used today. Cecilia Payne-Gaposchkin, as a Radcliffe graduate student, used Cannon's classifications to discover the composition of stars. Each built on the previous woman's work. None were permitted the title of astronomer until late in their careers or after their deaths.