A Rogue Planet Hypothesis for the Formation of the Trans-Neptunian Solar System ―太陽系外縁の形成におけるローグ惑星仮説―
Speaker: Yukun Huang
Abstract:
Over the past two decades, our knowledge of the Solar System’s Trans-Neptunian 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 distant Kuiper Belt beyond 50~au, 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, known as Sednoids. I will demonstrate in this talk, that a super-Earth-mass planet temporarily present in the Solar System (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, when examining the past history of the three Sednoids, I surprisingly find that all their apsidal lines were tightly clustered at 200° exactly 4.5 Gyr ago. This “primordial orbital alignment”, if confirmed true, strongly argues for an initial event that imprinted this particular apsidal orientation on early detached TNO population, and the rogue planet model could potentially explain this new phenomenon.