Orbital stability of coplanar two-planet exosystems with high eccentricities

TL;DR

This paper investigates the long-term stability of two-planet exosystems with high eccentricities using dynamical maps, resonances, and periodic orbits, revealing stable regions even at eccentricities above 0.5.

Contribution

It introduces a methodology combining dynamical maps and periodic orbit analysis to identify stable regions in highly eccentric two-planet systems, including observed exoplanets.

Findings

Stable regions exist in mean motion resonances for high eccentricities.

Elliptic periodic orbits correlate with long-term stability.

Application to observed exoplanets shows consistency with stability predictions.

Abstract

The long-term stability of the evolution of two-planet systems is considered by using the general three body problem (GTBP). Our study is focused on the stability of systems with adjacent orbits when at least one of them is highly eccentric. In these cases, in order for close encounters, which destabilize the planetary systems, to be avoided, phase protection mechanisms should be considered. Additionally, since the GTBP is a non-integrable system, chaos may also cause the destabilization of the system after a long time interval. By computing dynamical maps, based on Fast Lyapunov Indicator, we reveal regions in phase space with stable orbits even for very high eccentricities (e>0.5). Such regions are present in mean motion resonances (MMR). We can determine the position of the exact MMR through the computation of families of periodic orbits in a rotating frame. Elliptic periodic orbits are associated with the presence of apsidal corotation resonances (ACR). When such solutions are stable, they are associated with neighbouring domains of initial conditions that provide long-term stability. We apply our methodology so that the evolution of planetary systems of highly eccentric orbits is assigned to the existence of such stable domains. Particularly, we study the orbital evolution of the extrasolar systems HD 82943, HD 3651, HD 7449, HD 89744 and HD 102272 and discuss the consistency between the orbital elements provided by the observations and the dynamical stability.