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 876 d has a tidal Q ∼ 104-105, a value characteristic of solar system gas giants.
- Publication:
-
The Astronomical Journal
- Pub Date:
- April 2018
- DOI:
- 10.3847/1538-3881/aab09f
- arXiv:
- arXiv:1802.08385
- Bibcode:
- 2018AJ....155..157P
- Keywords:
-
- chaos;
- planetary systems;
- planets and satellites: dynamical evolution and stability;
- Astrophysics - Earth and Planetary Astrophysics
- E-Print:
- 6 pages, 5 figures, accepted to AJ