Survival of non-coplanar, closely-packed planetary systems after a close encounter

TL;DR

This study uses N-body simulations to analyze the stability and evolution of non-coplanar, closely-packed planetary systems after close encounters, revealing that many systems with inclinations survive longer than previously expected.

Contribution

It provides new insights into the long-term stability of inclined planetary systems following close encounters, highlighting the importance of initial inclinations and system scale.

Findings

Many inclined systems survive long after close encounters.

Survival time depends on initial inclination and system scale.

Inclined systems can evolve over 1,000 times longer than the encounter time.

Abstract

Planetary systems with more than two bodies will experience orbital crossings at a time related to the initial orbital separations of the planets. After a crossing, the system enters a period of chaotic evolution ending in the reshaping of the system's architecture via planetary collisions or ejections. We carry out N-body integrations on a large number of systems with equally-spaced planets (in units of the Hill radius) to determine the distribution of instability times for a given planet separation. We investigate both the time to the initiation of instability through a close encounter and the time to a planet-planet collision. We find that a significant portion of systems with non-zero mutual inclinations survive after a close encounter and do not promptly experience a planet-planet collision. Systems with significant inclinations can continue to evolve for over 1,000 times longer than the encounter time. The fraction of long lived systems is dependent on the absolute system scale and the initial inclination of the planets. These results have implications to the assumed stability of observed planetary systems.