The William Henry Pickering reference article from the English Wikipedia on 24-Apr-2004 (provided by Fixed Reference: snapshots of Wikipedia from wikipedia.org)

William Henry Pickering

William Henry Pickering (February 15, 1858 – January 17, 1938) was an American astronomer, brother of Edward Charles Pickering. Not to be confused with William Hayward Pickering, former director of the Jet Propulsion Laboratory.

He discovered Saturn's moon Phoebe.

He led solar eclipse expeditions and studied craters on the Moon. Constructed and established several observatories or astronomical observation stations, notably including Percival Lowell's Flagstaff Observatory.

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.

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