younger brother of E. C. Pickering. He assisted P. Lowell in establishing the Flagstaff Observatory, but later disagreed with Lowell’s exotic theories about life on Mars. From Harvard College Observatory’s southern station in Peru, Pickering discovered Saturn’s satellite Phoebe in 1898. His photographic lunar atlas was published in 1903. Pickering made many predictions of trans-Neptunian planets; a photographic search based on one of them recorded Pluto in 1919, but it was not identified at the time.