In the 1840s, with the help of Newtonian mechanics, Urbain Le Verrier predicted the position of the then undetected planet Neptune based on an analysis of perturbations of the orbit of Uranus. Subsequent observations of Neptune at the end of the 19th century led astronomers to suggest that, in addition to Neptune, another planet also has an impact on the orbit of Uranus. In 1906, Percival Lowell, a wealthy resident of Boston who founded the Lowell Observatory in 1894, initiated an extensive project to find the ninth planet in the solar system, which he named Planet X. By 1909, Lowell and William Henry Pickering had suggested several possible celestial coordinates for this planet. Lowell and his observatory continued to search for the planet until his death in 1916, but to no avail. In fact, on March 19, 1915, two low-level images of Pluto were obtained at his observatory without Lowell’s knowledge, but he was not recognized on them.
Mount Wilson Observatory could also claim the discovery of Pluto in 1919. That year, Milton Humason, on behalf of William Pickering, searched for the ninth planet, and Pluto’s image fell on a photographic Continue reading