Born on 15 May 1857 in Dundee, Scotland, Williamina Paton Stevens Fleming was a pioneering astronomer who devised a stellar classification system and discovered the Horsehead Nebula. In 1878 she immigrated to the US with her husband, who then abandoned her when she became pregnant. To support herself and her child, Fleming went to work as a maid in 1879 in the home of Edward Pickering, director of the Harvard College Observatory. Within two years Pickering hired her to work at the observatory as a human computer, part of a famed team of women known as the Harvard computers. There Fleming analyzed data about stellar spectra recorded on photographic plates. Over the next three decades, she developed a new stellar classification system and cataloged more than 10 000 stars. She discovered hundreds of variable stars, 10 novae, and 52 nebulae, including the Horsehead Nebula. And she was among the first to recognize the existence of white dwarfs. Fleming hired and supervised dozens of fellow female computers, including Annie Jump Cannon, Henrietta Swan Leavitt, and Antonia Maury, who became accomplished astronomers in their own right. (Cannon would go on to simplify Fleming’s stellar classification scheme.) Fleming coauthored a number of publications, among them the Draper Catalogue of Stellar Spectra (1890), “A photographic study of variable stars” (1907), and “Stars having peculiar spectra” (1912). In 1899 Fleming was given the title of curator of astronomical photographs at Harvard. In 1906 she became the first American woman to be made an honorary member of the Royal Astronomical Society of London. Shortly before her death, the Astronomical Society of Mexico awarded her the Guadalupe Almendaro medal for her discovery of new stars. Fleming died of pneumonia in Boston at age 54 in 1911. (Photo credit: Harvard College Observatory, courtesy AIP Emilio Segrè Visual Archives)
