Who was the American astronomer involved in the search for a planet thought to explain apparent discrepancies in the orbits of the giant planets?
Carl Otto Lampland: Carl Otto Lampland (December 29, 1873 – December 14, 1951) was an American astronomer. Carl Otto Lampland:  He was involved with both of the Lowell Observatory solar system projects, observations of the planet Mars and the search for Planet X. Planets beyond Neptune:  The search began in the mid-19th century and culminated at the start of the 20th with Percival Lowell's quest for Planet X. Lowell proposed the Planet X hypothesis to explain apparent discrepancies in the orbits of the giant planets, particularly Uranus and Neptune, speculating that the gravity of a large unseen ninth planet could have perturbed Uranus enough to account for the irregularities.
Carl Otto Lampland