Full-lifetime simulations of multiple unequal-mass planets across all phases of stellar evolution

TL;DR

This study performs extensive long-term simulations of multi-planet systems with unequal masses across all stellar evolution phases, revealing how mass dispersion influences planetary dynamics and stability around white dwarfs.

Contribution

It introduces the first comprehensive simulations of unequal-mass planetary systems over a Hubble time, linking stellar evolution phases self-consistently.

Findings

Increased mass dispersion reduces close encounters near white dwarfs.

Terrestrial-mass planets significantly influence system dynamics.

Instabilities during the white dwarf phase are as likely in unequal-mass systems as in equal-mass ones.

Abstract

We know that planetary systems are just as common around white dwarfs as around main sequence stars. However, self-consistently linking a planetary system across these two phases of stellar evolution through the violent giant branch poses computational challenges, and previous studies restricted architectures to equal-mass planets. Here, we remove this constraint and perform over 450 numerical integrations over a Hubble time (14 Gyr) of packed planetary systems with unequal-mass planets. We characterize the resulting trends as a function of planet order and mass. We find that intrusive radial incursions in the vicinity of the white dwarf become less likely as the dispersion amongst planet masses increases. The orbital meandering which may sustain a sufficiently dynamic environment around a white dwarf to explain observations is more dependent on the presence of terrestrial-mass planets than any variation in planetary mass. Triggering unpacking or instability during the white dwarf phase is comparably easy for systems of unequal-mass planets and systems of equal-mass planets; instabilities during the giant branch phase remain rare and require fine-tuning of initial conditions. We list the key dynamical features of each simulation individually as a potential guide for upcoming discoveries.