Circularizing Planet Nine through dynamical friction with an extended, cold planetesimal belt

Abstract

Unexpected clustering in the orbital elements of minor bodies beyond the Kuiper belt has led to speculations that our solar system actually hosts nine planets, the eight established plus a hypothetical "Planet Nine". Several recent studies have shown that a planet with a mass of about 10 Earth masses on a distant eccentric orbit with perihelion far beyond the Kuiper belt could create and maintain this clustering. The evolutionary path resulting in an orbit such as the one suggested for Planet Nine is nevertheless not easily explained. Here we investigate whether a planet scattered away from the giant-planet region could be lifted to an orbit similar to the one suggested for Planet Nine through dynamical friction with a cold, distant planetesimal belt. Recent simulations of planetesimal formation via the streaming instability suggest that planetesimals can readily form beyond 100au. We explore this circularisation by dynamical friction with a set of numerical simulations. We find that a planet that is scattered from the region close to Neptune onto an eccentric orbit has a 20-30% chance of obtaining an orbit similar to that of Planet Nine after 4.6Gyr. Our simulations also result in strong or partial clustering of the planetesimals; however, whether or not this clustering is observable depends on the location of the inner edge of the planetesimal belt. If the inner edge is located at 200au the degree of clustering amongst observable objects is significant.

Accepted to MNRAS

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Cited by in corpus (11)

• The Planet Nine Hypothesis
• Discovery and Dynamical Analysis of an Extreme Trans-Neptunian Object with a High Orbital Inclination
• Shepherding in a Self-Gravitating Disk of Trans-Neptunian Objects
• The Secular Dynamics of TNOs and Planet Nine Interactions
• The Generation of the Distant Kuiper Belt by Planet Nine from an Initially Broad Perihelion Distribution
• Stellar Flybys Interrupting Planet-Planet Scattering Generates Oort Planets
• Tilting Uranus via Secular Spin-Orbit Resonance with Planet 9
• The Resonance Hopping Effect in the Neptune-Planet Nine System
• On the origin of extreme trans-Neptunian objects within Modified Newtonian Dynamics
• The Influence of Planet 9 on the Orbits of Distant TNOs: The Case for a Low Perihelion Planet
• Very-wide-orbit planets from dynamical instabilities during the stellar birth cluster phase