who worked in the USA. At Harvard, working with E. C. Pickering, she established herself from 1881 as the most prominent woman astronomer of her time. Her major achievement was the classification of 10 351 stars according to their spectra in the Draper Catalogue of Stellar Spectra (1890), a forerunner of the Henry Draper Catalogue. Her scheme had 17 categories, an enormous improvement on P. A. Secchi’s pioneering scheme (see secchi classification); it was in turn refined by A. J. Cannon.