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UBC Theses and Dissertations

Dynamics of transneptunian objects under the influence of a rogue planet Huang, Yukun


Over the past two decades, our knowledge of the Solar System’s transneptunian region (often called the Kuiper Belt) has been gradually increasing. Observational surveys have greatly expanded the inventory of Trans-Neptunian Objects (TNOs), which are distant icy bodies thought to be relics from the giant planet formation era. In the main Kuiper Belt region, a complex bimodal inclination structure is present, leading to the common assertion that current TNOs may have accreted in different regions of the protoplanetary disk. To study this blended inclination structure, I develop an improved semi-analytical method to compute TNO ‘free’ inclinations, which are well conserved and thus better represent the primordial inclination profile. In the implanted Kuiper Belt, a semimajor axis power law distribution is observed in the outer Solar System surveys. I show that in a patched-conic model, the power law is a natural outcome after multiple flybys of the perturbing planet homogenize the directions of planetary relative-velocity vectors. This model allows one to analytically compute the diffusion coefficient in closed form. In the distant Kuiper Belt, several striking features seem to challenge our previous understanding of the early Solar System: 1) a very large population of objects in distant mean-motion resonances with Neptune, 2) a substantial detached population that are not dynamically coupled with Neptune’s effects, and 3) the existence of three very-large perihelion objects. I demonstrated in this thesis, that a super-Earth-mass planet temporarily present in the Solar System on a Neptune crossing orbit (referred to as a ‘Rogue Planet’), is able to create all these structures in the distant Kuiper Belt. Such a planet would have formed in the giant planet region and gotten scattered to a highly-eccentric orbit with a few hundred au semimajor axis with a typical lifetime of 100 Myr. Additionally, I showed this transient planet would not have heated the cold belt’s very low free inclinations to larger than observed. Both the structures in the distant belt and the existence of an unheated cold belt provide constraints to narrow down the mass and possible dynamical histories the rogue might have taken.

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