This work demonstrates that the long-term stability of the giant-planet system is governed not by smooth, adiabatic stellar mass loss but by the granularity of mass ejection during the Sun’s giant-branch evolution. Observationally inferred white-dwarf recoil velocities of roughly 0.75 km s−1 require many discrete, asymmetric ejections - plumes launched by pulsation-assisted convection - that impart small, randomly directed kicks to the Sun. Under smooth mass loss the four giant planets simply expand their semimajor axes by the factor M⋆,0/M⋆,f ≃ 1.85 (the Sun losing ≈46% of its mass to a ≈0.538 M⊙ white dwarf) while preserving period ratios and secular architecture; classical stability estimates therefore remain intact only for that idealized case.
Numerical N-body experiments incorporating stochastic, parcelized mass loss show a radically different outcome. Impulsive, randomly directed stellar recoils make every heliocentric orbit undergo a random walk whose amplitude is set by the ejection granularity. At parcel masses consistent with observed kicks, orbit crossings begin already on the red-giant branch: ~40% of realizations experience disruption or violent scattering before white-dwarf formation and ~90% self-destruct within 3 Gyr. The effective dynamical lifetime of the outer solar system thus collapses from ~10^18 yr (intrinsic chaos) to roughly a gigayear after white-dwarf formation, making terminal instability a direct consequence of stochastic mass loss.
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