William Henry Pickering (1858-1938), US astronomer and planetary scientist. Pickering predicted the existence of seven extra hypothetical planets in the solar system during using graphical analysis of perturbations in the orbits of known planets. He named them O, P, Q, R, S, T and U. He revised his results several times to fit observed data better, but planets have never been found that matched his predictions. He obtained some of the first photographs of Mars and used these as evidence that the supposed canals on Mars were actually natural features. In 1898 he found Saturn's ninth moon, Phoebe; this was the first satellite to be discovered using photographic means. Photographed 16 October 1909.