The Fate of Exomoons when Planets Scatter [skyandtelescope.com]
Planet interactions are thought to be common as solar systems are first forming and settling down. A new study suggests that these close encounters could have a significant impact on the moons of giant exoplanets — and they may generate a large population of free-floating exomoons.
[...] Led by Yu-Cian Hong (Cornell University), a team of scientists has now explored the fate of exomoons in planet–planet scattering situations using a suite of N-body numerical simulations. Hong and collaborators find that the vast majority — roughly 80 to 90% — of exomoons around giant planets are destabilized during scattering and don't survive in their original place in the solar system. Fates of these destabilized exomoons include:
- moon collision with the star or a planet,
- moon capture by the perturbing planet,
- moon ejection from the solar system,
- ejection of the entire planet–moon system from the solar system, and
- moon perturbation onto a new heliocentric orbit as a "planet".
[...] An intriguing consequence of Hong and collaborators' results is the prediction of a population of free-floating exomoons that were ejected from solar systems during planet–planet scattering and now wander through the universe alone. According to the authors' models, there may be as many of these free-floating exomoons as there are stars in the universe!
Innocent Bystanders: Orbital Dynamics of Exomoons During Planet–Planet Scattering [iop.org] (DOI: 10.3847/1538-4357/aaa0db) (DX [doi.org])