Pickering, William Henry, 1858–1938, American astronomer, b. Boston, grad. Massachusetts Institute of Technology (B.S., 1879). He taught at the Massachusetts Institute of Technology (1880–87) and at Harvard Observatory. Between 1878 and 1901 he led five solar eclipse expeditions and established several observatories and astronomical stations. Pickering discovered (1899) the ninth satellite of Saturn, called Phoebe, and also announced (1905) the finding of a tenth satellite, which was not confirmed until 1967. In 1919 he predicted the existence and the location of a ninth planet; Pluto, discovered in 1930 and long regarded as the ninth planet, is now considered a dwarf planet. His observations of the moon, including the study of lunar craters, is of lasting importance. He also accomplished important work in photographing the planets and measuring their brightness. His later researches were devoted to Mars. In addition to a number of papers in astronomical journals, his publications include The Moon (1903), Lunar and Hawaiian Physical Features Compared (1906), and Mars (1921).
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