William Henry Pickering

Astronomer, born in Boston, Massachusetts, USA, the brother of Edward Charles Pickering. A Massachusetts Institute of Technology graduate, he joined Harvard's astronomy department (1887–1924). He pioneered dry-plate celestial photography and took important early photographs of Mars (1888) and the Moon (1900), and 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 Percival Lowell's work. He established Harvard observatories at Arequipa, Peru (1891) and in Jamaica (1900), and Percival Lowell's observatory at Flagstaff, AZ (1894).

William Henry Pickering (February 15, 1858 – January 17, 1938) was an American astronomer, brother of Edward Charles Pickering.

He discovered Saturn's ninth moon Phoebe in 1899 from plates taken in 1898.

He led solar eclipse expeditions and studied craters on the Moon, and hypothesized that changes in the appearance of the crater Eratosthenes were due to "lunar insects".

In 1919, he predicted the existence and position of a Planet X based on anomalies in the positions of Uranus and Neptune but a search of Mount Wilson Observatory photographs failed to find the predicted planet. Pluto was later discovered at Flagstaff by Clyde Tombaugh in 1930, but in any case it is now known that Pluto's mass is far too small to have appreciable gravitational effects on Uranus or Neptune, and the anomalies are accounted for when today's much more accurate values of planetary masses are used in calculating orbits.

He spent much of the later part of his life at his private observatory in Jamaica.

Pickering crater on the Moon is jointly named after him and his brother Edward Charles Pickering.