Reassessing the Source of Long-Period Comets

TL;DR

This study uses numerical simulations to identify the inner Oort Cloud as a significant source of long-period comets, providing constraints on its population and challenging its role in mass extinctions.

Contribution

It reveals a new dynamical pathway for inner Oort Cloud objects to become observable comets and constrains the population of the inner Oort Cloud based on observational data.

Findings

Inner Oort Cloud objects can reach Jupiter's orbit via a new dynamical pathway.

The population of the inner Oort Cloud is consistent with giant planet formation theories.

Only one significant comet shower has likely occurred since the Cambrian Explosion.

Abstract

We present numerical simulations to model the production of observable long-period comets (LPCs) from the Oort Cloud, a vast reservoir of icy bodies surrounding the Sun. We show that inner Oort Cloud objects can penetrate Jupiter's orbit via a largely unexplored dynamical pathway, and they are an important, if not the dominant, source of known LPCs. We use this LPC production to place observationally motivated constraints on the population and mass of the inner Oort Cloud, which are consistent with giant planet formation theory. These constraints indicate that only one comet shower producing late Eocene bombardment levels has likely occurred since the Cambrian Explosion, making these phenomena an improbable cause of additional extinction events.