A Rogue Planet Populated the Distant Kuiper Belt

The orbital distribution of trans-Neptunian objects (TNOs) in the distant Kuiper Belt (with semimajor axes beyond the 2:1 resonance, roughly a > 50 au) provides constraints on the dynamical history of the outer solar system. Recent studies have shown two striking features of this region: 1) a very large population of objects in distant mean-motion resonances with Neptune, and 2) the existence of a substantial detached population (non-resonant objects largely decoupled from Neptune). While various Neptune migration models are able to implant some resonant and detached objects during the planet formation era, they fail to match a variety of aspects of the orbital distribution in the distant Kuiper Belt. In this work, we report simulations that are carried out using an improved version of the GPU based code GLISSE (Zhang & Gladman 2022), following 100,000 test particles per simulation in parallel while handling their planetary close encounters. We demonstrate for the first time that a 2 Earth–mass rogue planet temporarily present during planet formation can abundantly populate both the distant resonances and the detached populations, even without any planetary migration. We show how weak encounters with the rogue increase the efficiency of filling the resonances, while also dislodging objects out of resonances at high perihelia. Its secular effect simultaneously generates numerous detached objects observed at all semimajor axes. These results suggest that the early presence of an additional planet reproduces the observed TNO orbital structure in the distant Kuiper Belt.