1906-1998

American astronomer who discovered the planet Pluto. Tombaugh helped Lowell Observatory director Vesto Slipher search for a new planet. The previous director, Percival Lowell, had suggested the possible location of a planet affecting the orbits of Uranus and Neptune. Tombaugh studied photographs taken of that site at different times, looking for light and movement varying from that of stars. On February 18, 1930, he detected such movement in the Gemini constellation, and the discovery of Pluto was publicized the next month.