Planet-Planet Tides in the TRAPPIST-1 System

Abstract

The star TRAPPIST-1 hosts a system of seven transiting, terrestrial exoplanets apparently in a resonant chain, at least some of which are in or near the Habitable Zone. Many have examined the roles of tides in this system, as tidal dissipation of the orbital energy of the planets may be relevant to both the rotational and orbital dynamics of the planets, as well as their habitability. Generally, tides are calculated as being due to the tides raised on the planets by the star, and tides raised on the star by the planets. I write this research note to point out a tidal effect that may be at least as important as the others in the TRAPPIST-1 system and which is so far unremarked upon in the literature: planet-planet tides. Under some reasonable assumptions, I find that for every planet $p$ in the TRAPPIST-1 system there exists some other planet $q$ for which the planet-planet dynamical tidal strain is within an order of magnitude of the stellar eccentricity tidal strain, and that the effects of planet $f$ on planet $g$ are in fact greater than that of the star on planet $g$. It is thus not obvious that planet-planet tides can be neglected in the TRAPPIST-1 exoplanetary system, especially the tides on planet $g$ due to planet $f$, if the planets are in synchronous rotation.

3 pp Research Note of the AAS. v.2 contains additional citation to prior art by Lingam & Loeb (2018) Astrobiology 18, 967

References in corpus (7)

• Seven temperate terrestrial planets around the nearby ultracool dwarf star TRAPPIST-1
• The nature of the TRAPPIST-1 exoplanets
• Stellar parameters for TRAPPIST-1
• The TRAPPIST-1 system: Orbital evolution, tidal dissipation, formation and habitability
• Spin-orbital tidal dynamics and tidal heating in the TRAPPIST-1 multi-planet system
• Oceanic tides from Earth-like to ocean planets
• Habitability from Tidally-Induced Tectonics

Cited by in corpus (6)

• A review of possible planetary atmospheres in the TRAPPIST-1 system
• Tides between the TRAPPIST-1 planets
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• Survival and dynamics of rings of co-orbital planets under perturbations
• Atmospheric gravitational tides of Earth-like planets orbiting low-mass stars
• Disentangling Atmospheric Compositions of K2-18 b with Next Generation Facilities