The Formation of the Oort Cloud in Open Cluster Environments

TL;DR

This study investigates how the Sun's early environment in open clusters influences the formation and structure of the Oort cloud through simulations, revealing environmental effects on comet distribution and potential observational signatures.

Contribution

It provides the first detailed simulations of Oort Cloud formation in open cluster environments, highlighting differences from field formation models and implications for early Solar System conditions.

Findings

Inner Oort Cloud is loaded with comets during cluster residence

Outer Oort Cloud trapping efficiencies are about half of previous models

Some simulations match observed extended scattered disk orbits

Abstract

We study the influence of an open cluster environment on the formation and current structure of the Oort cloud. To do this, we have run 19 different simulations of the formation of the Oort Cloud for 4.5 Gyrs. In each simulation, the solar system spends its first 100 Myrs in a different open cluster environment before transitioning to its current field environment. We find that, compared to forming in the field environment, the inner Oort Cloud is preferentially loaded with comets while the Sun resides in the open cluster and that most of this material remains locked in the interior of the cloud for the next 4.4 Gyrs. In addition, the outer Oort Cloud trapping efficiencies we observe in our simulations are lower than previous formation models by about a factor of 2, possibly implying an even more massive early planetesimal disk. Furthermore, some of our simulations reproduce the orbits of observed extended scattered disk objects, which may serve as an observational constraint on the Sun's early environment. Depending on the particular open cluster environment, the properties of the inner Oort Cloud and extended scattered disk can vary widely. On the other hand, the outer portions of the Oort Cloud in each of our simulations are all similar.