Predicting multiple planet stability and habitable zone companions in the TESS era

Abstract

We present an approach that is able to both rapidly assess the dynamical stability of multiple planet systems, and determine whether an exoplanet system would be capable of hosting a dynamically stable Earth-mass companion in its habitable zone (HZ). We conduct a suite of numerical simulations using a swarm of massless test particles (TPs) in the vicinity of the orbit of a massive planet, in order to develop a predictive tool which can be used to achieve these desired outcomes. In this work, we outline both the numerical methods we used to develop the tool, and demonstrate its use. We find that the TPs survive in systems either because they are unperturbed due to being so far removed from the massive planet, or due to being trapped in stablemean-motion resonant orbits with themassive planet. The resulting unexcited TP swarm produces a unique signature in (a, e) space that represents the stable regions within the system. We are able to scale and translate this stability signature, and combine several together in order to conservatively assess the dynamical stability of newly discovered multiple planet systems. We also assess the stability of a system's HZ and determine whether an Earth-mass companion could remain on a stable orbit, without the need for exhaustive numerical simulations.