Dynamical Interactions Make Hot Jupiters in Open Star Clusters

TL;DR

This study uses N-body simulations to demonstrate that dynamical interactions in star clusters can frequently produce hot Jupiters from planets initially far from their host stars, often accompanied by distant eccentric gas giants.

Contribution

It provides the first detailed simulation-based evidence that hot Jupiters can form dynamically within star clusters, highlighting a new formation pathway.

Findings

Hot Jupiters can form frequently inside star clusters due to dynamical interactions.

Simulated hot Jupiters have orbital characteristics similar to some observed extreme exoplanets.

Many hot Jupiters formed are accompanied by distant, eccentric gas giants.

Abstract

Explaining the origin and evolution of exoplanetary "hot Jupiters" remains a significant challenge. One possible mechanism for their production is planet-planet interactions, which produces hot Jupiters from planets born far from their host stars but near their dynamical stability limits. In the much more likely case of planets born far from their dynamical stability limits, can hot Jupiters can be formed in star clusters? Our N-body simulations of planetary systems inside star clusters answer this question in the affirmative, and show that hot Jupiter formation is not a rare event. We detail three case studies of the dynamics-induced births of hot Jupiters on highly eccentric orbits that can only occur inside star clusters. The hot Jupiters' orbits bear remarkable similarities to those of some of the most extreme exoplanets known: HAT-P-32 b, HAT-P-2 b, HD 80606 b and GJ 876 d. If stellar perturbations formed these hot Jupiters then our simulations predict that these very hot, inner planets are often accompanied by much more distant gas giants in highly eccentric orbits.