A Lopsided Outer Solar System

TL;DR

This paper demonstrates that a primordial scattered disk in the outer solar system can develop a lopsided, asymmetric structure due to gravitational instabilities, influenced by planetary forces, similar to galactic bar formation.

Contribution

It extends the understanding of disk instabilities by showing that outer solar system disks can exhibit lopsided modes influenced by giant planets, using a mechanism analogous to galactic bar formation.

Findings

Outer solar system disks can become lopsided due to gravitational instabilities.

Surface density and velocity plots show formation of concentric and spiral structures.

The dynamics are explained using Lynden-Bell's bar formation mechanism.

Abstract

Axisymmetric disks of eccentric orbits in near-Keplerian potentials are unstable to an out-of-plane buckling. Recently, Zderic et al. (2020) showed that an idealized disk saturates to a lopsided mode. Here we show that this apsidal clustering also occurs in a primordial scattered disk in the outer solar system which includes the orbit-averaged gravitational influence of the giant planets. We explain the dynamics using Lynden-Bell (1979)'s mechanism for bar formation in galaxies. We also show surface density and line of sight velocity plots at different times during the instability, highlighting the formation of concentric circles and spiral arms in velocity space.