Life in the dark: Potential urability of moons of rogue planets

TL;DR

This study investigates the potential for moons of rogue planets to sustain internal heat through tidal dissipation after supernova ejection, possibly creating habitable environments without stellar radiation.

Contribution

It demonstrates that moons can remain bound and retain eccentricity post-supernova, enabling long-term tidal heating capable of supporting subsurface oceans, a novel insight into astrobiological potential of rogue planet moons.

Findings

Moons survive supernova explosions and stay gravitationally bound.

Eccentricities up to 0.007 for single moons, 0.02 for resonant pairs are excited.

Tidal heating can be sufficient to maintain liquid oceans beneath ice crusts.

Abstract

Free-floating planets are thought to be numerous in the Galaxy and may retain their moons after ejection from their natal systems. If those satellites acquire or preserve orbital eccentricity, tidal dissipation could provide a long-lasting internal heat source, potentially creating urable environments (capable of enabling abiogenesis) in the absence of stellar radiation. We explore (i) whether moons remain bound to planets expelled by a core-collapse supernova, (ii) how the explosion reshapes their orbits, and (iii) under which circumstances tidal heating can sustain urable subsurface oceans. We carried out three-dimensional N-body simulations with an 8th-order Runge-Kutta scheme, modelling homologous stellar mass loss for progenitors of 10 M$_{\odot}$. Post-explosion orbital elements of single moons and resonant moon systems were analysed, and tidal heating power was estimated with a constant phase-lag model for several tidal dissipation functions and moon densities. All simulated moons survive the supernova and remain bound to their planets. The explosion excites moon eccentricities up to $\sim7\times10^{-4}$ and $\sim3\times10^{-3}$ for single moons of planets with circular and eccentric orbits, respectively. For resonant pairs, an eccentricity of $\leq2\times10^{-2}$ is preserved. The semi-major axis of the moons changes by $\leq0.2\%$. For 12-15\% of cases -- preferentially moons at $a\leq15\,R_{\mathrm{planet}}$ and with $e\geq10^{-3}$ -- the specific tidal heating power lies between 0.1 and 10 times what is estimated on Europa or Enceladus, sufficient to maintain liquid oceans beneath an ice crust. Eccentricity damping timescales exceed the age of the Solar System for $a\geq10\,R_{\mathrm{planet}}$, implying billions of years of continuous heating on the moons. Such worlds represent promising targets for future searches for extraterrestrial life.