The Influence of Outer Solar System Architecture on the Structure and Evolution of the Oort Cloud

TL;DR

This study investigates how the architecture of the outer Solar System influences the structure and evolution of the Oort Cloud and the flux of Earth-crossing comets, highlighting the role of giant planets as planetary protectors.

Contribution

It provides a comprehensive simulation-based analysis of how different planetary mass configurations affect the Oort Cloud's structure and comet flux, incorporating the full age of the Solar System.

Findings

Decreased planetary mass increases comet trapping efficiency.

Systems with Saturn-mass objects better deflect Earth-crossing comets.

Overall OC structure remains stable across different planetary configurations.

Abstract

We study the influence of outer Solar System architecture on the structural evolution of the Oort Cloud (OC) and the flux of Earth-crossing comets. In particular, we seek to quantify the role of the giant planets as "planetary protectors". To do so, we have run simulations in each of four different planetary mass configurations to understand the significance of each of the giant planets. Because the outer planets modify the structure of the OC throughout its formation, we integrate each simulation over the full age of the Solar System. Over this time, we follow the evolution of cometary orbits from their starting point in the protoplanetary disk to their injection into the OC to their possible re-entry into the inner planetary region. We find that the overall structure of the OC, including the location of boundaries and the relative number of comets in the inner and outer parts, does not change significantly between configurations; however, as planetary mass decreases, the trapping efficiency (TE) of comets into the OC and the flux of comets into the observable region increases. We determine that those comets that evolve onto Earth-crossing orbits come primarily from the inner OC but show no preference for initial protoplanetary disk location. We also find that systems that have at least a Saturn-mass object are effective at deflecting possible Earth-crossing comets but the difference in flux between systems with and without such a planet is less than an order of magnitude. We conclude by discussing the individual roles of the planets and the implications of incorporating more realistic planetary accretion and migration scenarios into simulations, particularly on existing discrepancies between low TE and the mass of the protoplanetary disk and on determining the structural boundaries of the OC.