Chaotic Excitation and Tidal Damping in the GJ 876 System

Abstract

The M-dwarf GJ 876 is the closest known star to harbor a multi-planetary system. With three outer planets locked in a chaotic Laplace-type resonance and an appreciably eccentric short-period Super-Earth, this system represents a unique exposition of extrasolar planetary dynamics. A key question that concerns the long-term evolution of this system, and the fate of close-in planets in general, is how the significant eccentricity of the inner-most planet is maintained against tidal circularization on timescales comparable to the age of the universe. Here, we employ stochastic secular perturbation theory and N-body simulations to show that the orbit of the inner-most planet is shaped by a delicate balance between extrinsic chaotic forcing and tidal dissipation. As such, the planet's orbital eccentricity represents an indirect measure of its tidal quality factor. Based on the system's present-day architecture, we estimate that the extrasolar Super-Earth GJ 876d has a tidal Q~10,000-100,000 - a value characteristic of solar system gas giants.

6 pages, 5 figures, accepted to AJ

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• A Tidal Origin for a 3-body Resonance in Kepler-221
• Formation of a planetary Laplace resonance through migration in an eccentric disk - The case of GJ876
• Long-term tidal evolution of the TRAPPIST-1 system
• TOI-5108 b and TOI 5786 b: Two transiting sub-Saturns detected and characterized with TESS, MaHPS and SOPHIE
• Interactions Among Non-Interacting Particles in Planet Formation Simulations
• Exploring Exoplanet Dynamics with JWST: Tides, Rotation, Rings, and Moons
• The Formation of Double Hot Jupiter Systems through von Zeipel-Lidov-Kozai Migration
• Super-earths and mini-neptunes follow different orbital period-eccentricity relations
• TOI-1634 b: an Ultra-Short Period Keystone Planet Sitting Inside the M Dwarf Radius Valley
• How to measure tidal dissipation in long resonant chains