I hope you've heard of Tyche, the giant 5th gas giant in the Oort Cloud proposed by Dan Whitemire and John Matesee that's believed to have been gathered from data by WISE.Most astronomers agree that long-period comets (those with orbits of thousands to millions of years) have a roughly isotropic distribution; that is, they arrive at random from every point in the sky. Because comets are volatile and dissipate over time, astronomers suspect that they must be held in a spherical cloud tens of thousands of AU distant (known as the Oort cloud) for most of their existence. However, Matese and Whitmire claimed that rather than arriving from random points across the sky as is commonly thought, comet orbits were in fact clustered in a band inclined to the orbital plane of the planets. It’s possible that large planets (bigger than Jupiter) are perturbing the orbits of comets with their gravity, clustering them and nudging these comets in our direction. One of these may be the famed Tyche. WISE and Voyager 1, the latter some 14873 AU from Tyche, may help add to the knowledge of these putative planets. This theory does have its flaws, though. Alan Boss of the Carnegie Institution in Washignton thinks that the giant planets formed in an instant when the dust and gas collapsed together in a process known as disc instability. According to his model, a 9th planet is unlikely to have formed far beyond the Kuiper Belt. The dust disc from which the solar system formed was no bigger than 100AU across, so a halo of planets 18000 AU away is virtually out of the question. Moreover, if there are large planets in the Oort Cloud, they would've severely affected the orbits of Pluto and Eris, which has not been observed. There might be a ice giant in the Oort Cloud, one the size of Uranus, maybe.