4.2. Evidence for Dark Matter as a Function of Scale Size

4.2.1. The Solar System

The first historical success of using perturbed motions to find matter was the discovery of Neptune from the observed perturbations in the motion of Uranus. Similar perturbations in the orbit of Neptune and Uranus were then used to predict the existence of a yet more distant planet. Those predictions were again verified with the discovery of Pluto in 1930 by Clyde Tombaugh, who, incidentally also discovered evidence for the existence of superclusters. These successes spurred on efforts to discover a planet beyond Pluto, known as Planet 10 as the combined masses of Neptune and Pluto weren't quite enough to account for the observed perturbations in the orbits of the outer planets. Interestingly, the close passage of Voyager II near Neptune in 1993 allowed for a significant refinement of the mass of Neptune. Voyager II determined a mass 15% larger than that which had been previously measured. This proper accounting of Neptune's mass removed the need for the existence of Planet X and indeed there is no longer any evidence for unaccounted mass in the Solar System (see also Hogg et al. 1991).