Astronomer. Her career achievements made a major contribution in the advancement of astronomy and, in addition to being noted for her discovery of the Horsehead Nebula in 1888, she helped develop a common designation system for stars and cataloging thousands of stars and other astronomical phenomena. She worked briefly as a teacher and shortly after her marriage, at the age of 21, moved to Boston, Massachusetts, USA. Soon after their arrival her husband abandoned her and it was necessary for her to find work in order to support herself and her new born son. It was her choice of job and employer that was to change her life. She worked as a maid in the home of Professor Edward Charles Pickering, the director of Harvard College Observatory (HCO) and the story told is that Pickering was frustrated with the performance of his male assistants and would complain loudly: ‘My Scottish maid could do better!’ In 1881 Pickering, an advocate of higher education for women and an exacting employer, hired her and taught her how to analyse stellar spectra. She soon demonstrated her flare for astronomy and it was not long before she devised a system for classifying stars according to the relative amount of hydrogen observed in their spectra. Her work at the observatory was so outstanding that she was put in charge of hiring and supervising a team of women to sort and study the immense collection of photographs of star spectra. Over the next 15 years, she hired 20 women, some of them were college graduates who had majored in astronomy and went on to become famous astronomers in their own right, including Antonia Maury, Henrietta Leavitt, and Annie Jump Cannon. In 1888 she discovered the Horsehead Nebula on a telescope-photogrammetry plate made by the astronomer W. H. Pickering, brother of E.C. Pickering. In 1899, she was made Curator of Astronomical Photographs at Harvard, and in 1906, she was made an honorary member of the Royal Astronomical Society of London, the first American woman to be so honoured. Soon after that she was appointed an honorary fellow in astronomy of Wellesley College. She published ‘A Photographic Study of Variable Stars’ in1907, her discovery of white dwarfs in 1910 and ‘Spectra and Photographic Magnitudes of Stars in Standard Regions’ in 1911.