The Planet discovered at Lowell Observatory

Abstract

LAST week I indicated the basis of Lowell's prediction of an unknown planet exterior to Neptune. Further consideration of Lowell's memoir leaves me of the opinion that the residuals in the motion of Uranus are too small for the orbit of a disturbing planet to be predicted with any certainty. It may be of interest to give the opinion of Newcomb, who, with his assistants, was responsible for the tables of all the major planets the positions of which are given in the Nautical Almanac. In the introduction to his tables of Uranus he wrote: “These tables of Uranus are based on elements derived from meridian observations of the planet from the time of its discovery by Herschel in 1781 to the opposition of 1898. The outstanding residuals between theory and observation, left in the solution of the equations, sometimes amount to one second of arc. It is not possible at the present time to decide whether these differences are real or whether they arise from the errors of the ephemeris of comparison, which, between 1830 and 1872, was that derived from Bouvard's tables. The observations since 1860 seem to be represented with great exactness.” No great importance need be placed on the fact that Lowell used three normal places earlier than 1781 and that he included observations up to 1910. In justice to him, however, it should be stated that he made no claim to very great accuracy in the prediction.