Solar Periodic Companion and Random Stellar Flybys: Dynamical Perturbations of Highly Eccentric Comets in the Oort Cloud

TL;DR

This paper investigates how stellar flybys and a potential long-period stellar companion influence the orbits of highly eccentric comets in the Oort Cloud, revealing increased comet-shower rates and linking the cloud's dynamics to the Sun's stellar birth environment.

Contribution

It combines analytical estimates, N-body simulations, and Gaia data to quantify stellar perturbations on the Oort Cloud and identifies a candidate stellar companion affecting comet activity.

Findings

Stellar flybys increase comet-shower rates by about 2 times per encounter.

A candidate star with 45 Myr perihelion passages could boost comet activity by an order of magnitude.

The Oort Cloud's structure may retain dynamical memory of the Sun's birth cluster.

Abstract

The Gaia space telescope has transformed our understanding of random stellar encounters with the Solar System. This study examines how such perturbations influence the most eccentric comets in the Oort Cloud (OC), a thermalized reservoir of $\sim 10^{12}$ icy bodies extending from $10^{4}$ to $10^{5}$ AU. Recent Gaia-based analyses indicate about 20 stellar passages within 1 pc of the Sun per Myr. Using analytical estimates and direct $N$-body simulations, we quantify how these encounters modify highly eccentric orbits: individual flybys enhance comet-shower rates by factors of about 2, producing a cumulative increase of roughly 40 over a Myr. In parallel, we perform a full dynamical search through all stars with six-dimensional phase-space data in Gaia DR3 and identify a compelling candidate for a long-period stellar companion to the Sun. This star exhibits recurrent $\sim 45$ Myr perihelion passages and, in simulations, can elevate comet-shower activity by an order of magnitude. Because a perturber of this kind could also be a dispersed solar sibling, the companion hypothesis links the dynamical structure of the OC directly to the long-standing problem of identifying the Sun's birth-cluster relatives. The chemical-abundance pattern of such a star therefore becomes a critical observational test. Together, these results clarify how both stochastic encounters and potential long-period companions shape the dynamical evolution and observable output of the outermost OC, while highlighting the possibility that the OC retains a dynamical memory of the Sun's earliest stellar environment.