Pickering, William Henry (1858–1938)

US astronomer. He pioneered dry-plate celestial photography and took important early photographs of Mars (1888) and the moon (1900). He was the first to discover a satellite by photography when he located Phoebe, Saturn's ninth moon (1899). His published analyses of Martian canals and his independent prediction of Pluto's existence (1919) rivalled the work of the astronomer Percival Lowell.

He was born in Boston, Massachusetts. A Massachusetts Institute of Technology graduate, he joined Harvard's astronomy department (1887–1924). Pickering established Harvard observatories at Arequipa, Peru (1891) and in Jamaica (1900), and Percival Lowell's observatory at Flagstaff, Arizona (1894).