William Henry Pickering
William Henry Pickering (February 15, 1858 – January 16, 1938) was an American astronomer. Pickering constructed and established several observatories or astronomical observation stations, notably including Percival Lowell's Flagstaff Observatory. 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". He spent much of the later part of his life at his private observatory in Jamaica.
William Henry Pickering
Pickering in 1909
|Born||February 15, 1858|
|Died||January 16, 1938 (aged 79)|
|Education||Massachusetts Institute of Technology (1897)|
|Awards||Lalande Prize (1905)|
Prix Jules Janssen (1909)
He believed he discovered a tenth moon in 1905 from plates taken in 1904, which he called "Themis". For this discovery he was awarded the Lalande Prize of the French Academy of Sciences in 1905. "Themis" was later shown to not exist.
Following George Darwin, he speculated in 1907 that the moon was once a part of the earth and that it broke away where now the Pacific Ocean lies. He also proposed a version of continental drift before Alfred Wegener where America, Asia, Africa, and Europe once formed a single continent, which broke up because of the separation of the moon. 
In 1908 he made a statement regarding the possibility of airplanes that had not yet been invented, saying that "a popular fantasy is to suppose that flying machines could be used to drop dynamite on the enemy in time of war".
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. When the planet was named, he interpreted its symbol as a monogram referring to himself and Lowell by the phrase "Pickering-Lowell".
He claimed to have found vegetation on the moon in 1921.
He won the Prix Lalande in 1905 and the Prix Jules Janssen in 1909. The asteroid 784 Pickeringia, and the craters Pickering on the Moon and Pickering on Mars, are jointly named after him and his brother Edward Charles Pickering.
- "William Henry Pickering". New International Encyclopedia. 18. 1918. p. 605.
He was born in Boston and in 1879 graduated from Massachusetts Institute of Technology, where he was an assistant and instructor in physics in 1880–1887. In the latter year he was appointed assistant professor of astronomy at the Harvard Observatory. Pickering led eclipse expeditions to Colorado (1878), Grenada (1886), California (1889), Chile (1893), and Georgia (1900); discovered Phoebe, the ninth satellite of Saturn, in 1899, and later Themis, the tenth satellite; made lunar observations in California in 1904; and visited Hawaii (1905) and the Azores (1907). He received the Lalande prize in 1905 and the Janssen medal in 1909. His publications include: Guide to Mount Washington Range (1882); The Moon (1903); Lunar and Hawaiian Physical Features Compared (1906)
- Moore, Patrick (1999). The wandering astronomer. Bristol; Philadelphia: Institute of Physics Pub. ISBN 9780750306935.
- "Book of Members, 1780–2010: Chapter P" (PDF). American Academy of Arts and Sciences. Retrieved 22 April 2011.
- William Henry Pickering (1907). "The Place of Origin of the Moon – The Volcani Problems". Popular Astronomy. 15: 274–287. Bibcode:1907PA.....15..274P.
- Pickering W. H. (1930). "The discovery of Pluto". Monthly Notices of the Royal Astronomical Society. 91 (1): 0812–0817. Bibcode:1931MNRAS..91..812P. doi:10.1093/mnras/91.7.812.
- "Says 2 Crops A Day Grow On The Moon. Prof. Pickering Is Convinced Markings Are Caused by Vegetation in the Craters. Field Patterns Traced. Criticises Astronomers for Assuming Life There Is Impossible. Easier to Study Than Mars" (PDF). The New York Times. October 9, 1921.
- "Prof. Pickering To Resign. Astronomer Will Be Made Assistant Professor Emeritus at Harvard". New York Times. June 28, 1923. Retrieved 2015-03-31.
- "Prof. Pickering, 79, Astronomer, Dead. Discoverer of Planet Phoebe in 1899 Is Stricken at Mandeville, Jamaica". New York Times. January 22, 1938. Retrieved 2015-03-31.
Professor William Henry Pickering died Monday at Mandeville Observatory, where he had lived for three decades. He was buried in Mandeville. His age was 79. ...