A dynamical origin for planets in triple star systems

TL;DR

This paper investigates how dynamical interactions, specifically binary-binary encounters in star clusters, can lead to the formation of planets in triple star systems, providing a possible origin for these observed exoplanets.

Contribution

It introduces a new dynamical formation scenario for planets in triple systems via binary-binary scattering in star clusters.

Findings

Probability of forming a planet-hosting triple via binary-binary scattering is 0.5-3%.

Binary-binary encounters are a viable formation pathway for planets in triples.

Upcoming TESS data will help test this formation scenario.

Abstract

Recent radial velocity and transit data discovered $\sim 100$ planets in binary or triple stellar systems out of the entire population of a few thousand known planets. Stellar companions are expected to strongly influence both the formation and the dynamical evolution of planets in multiple star systems. Here, we explore the possibility that planets in triples are formed as a consequence of the dynamical interactions of binaries in star clusters. Our simulations show that the probability of forming a planet-hosting triple as a consequence of a single binary-binary scattering is in the range $0.5-3\%$, when one of the binaries hosts a planet. Along with other formation scenarios, binary-binary encounters are a viable way of creating planet-hosting triple systems. The recently launched TESS satellite is expected to find a larger sample of planets in triple systems, and to shed light on their origin.