Free Astronomy Magazine September-October 2022

36 SEPTEMBER-OCTOBER 2022 ASTRO PUBLISHING T he six most distant known objects in the solar system, with orbits exclusively beyond that of Neptune (magenta-pink), all mysteriously line up in a single direction. Also, when viewed in 3D, they tilt nearly identically away from the plane of the solar system. Caltech’s Konstantin Batygin and Mike Brown have shown that a planet with 10 times the mass of the Earth in a dis- tant eccentric orbit anti-aligned with the other six objects (orange) is required to maintain this configuration. [Caltech/R. Hurt (IPAC)] without assuming the exis- tence of the phantom Planet X. A study of the measure- ments made by the Voyager 2 probe revealed that the ir- regularities observed in the motion of Uranus were sim- ply due to a slight overesti- mation of the mass of Nep- tune. Subsequent improve- ments in our understanding of the latter's orbit made the existence of another planet completely superflu- ous. Without a starting point in the form of gravita- tional perturbations of the outer planets, there was no longer any way to calculate to an acceptable approxima- tion the position in the sky of some possible Planet X and then go out and look for it. The most stubborn as- tronomers still searching for A predicted consequence of the existence of Planet Nine is that a second set of confined objects should also exist. These objects are forced into positions at right angles to Planet Nine and in orbits perpendicular to the plane of the solar system. Five known ob- jects (blue) fit this prediction exactly. [Caltech/R. Hurt (IPAC) − Diagram was created using WorldWide Telescope] Planet X could only make rough assump- tions about its mass and orbital properties given the instrumental, tem- poral and spatial limits of all the surveys carried out up to that time. A planet of 4-5 Earth masses at least 200 AU from the Sun, or a pro- portionately larger planet even further out, would have been unde- tectable using the tech- nology of the 1990s even in the infrared, the domain of wavelengths where a body so far away would be ex- pected to peak in its electromagnetic radia- tion. In the last thirty years, many works have been published that have placed further re- strictions on the exis-