Elizabeth Langdon Williams

Her precise calculations for Percival Lowell's "Planet X" project laid groundwork that helped locate what later became recognized as Pluto.

Elizabeth Langdon Williams (1879-1981) - American human computer and astronomer. Her complex orbit - calculations under Lowell Observatory's Planet X search contributed to the eventual discovery of Pluto.

Elizabeth Langdon Williams was born on February 8, 1879, in Putnam, Connecticut, United States. She graduated in 1903 from the Massachusetts Institute of Technology (MIT) with a degree in physics - among the earliest women to graduate from MIT. In 1905, she was hired by astronomer Percival Lowell to work in his Boston office, initially editing publications. Soon she became a "human computer": performing the laborious manual calculations needed for Lowell's hypothesized 21 "Planet X" - a yet - undiscovered planet believed to perturb the orbits of Neptune and Uranus. From about 1910, Williams served as head human computer for the Planet X program, calculating possible orbital parameters and sky positions for the unknown planet. After Lowell's death in 1916, the search was paused; but decades later - when the search resumed - astronomers used predictions stemming from her earlier calculations, which helped pinpoint the object that would be named Pluto in 1930. Williams moved in 1919 from Boston to the observatory in Flagstaff, Arizona, where she handled further calculations and administrative correspondence at the Lowell Observatory. In 1922 she married astronomer George Hall Hamilton; shortly after their marriage, both were dismissed from Lowell Observatory - as employing married women was then deemed inappropriate. The couple then worked for a time at a station of Harvard College Observatory in Mandeville, Jamaica. After her husband's death in 1935, Williams retired and eventually moved to New Hampshire, where she lived until her death in 1981 in Enfield, at the age of 101. Although her contributions were long underappreciated - overshadowed by social norms and the work of others - today Elizabeth Langdon Williams is recognized as an early - and critical - female astronomer whose calculations played a key role in one of the major discoveries of the Solar System.