Trajectory of the stellar flyby that shaped the outer Solar System

Unlike Solar System planets, numerous smaller bodies beyond Neptune exhibit eccentric orbits. While giant planet migration might explain some scattering, it doesn't account for distant trans-Neptunian objects (TNOs). A stellar flyby offers an alternative, but its parameter space is vast. This study compares observed TNO properties with thousands of flyby simulations, identifying a 0.8^+0.1_−0.1 *M*_⊙ star passing at 110 ± 10 au, inclined by 70°⁺⁵₋₁₀, as a near-perfect match. This flyby replicates the retrograde TNO population. Such flybys are reasonably frequent, and the Vera Rubin telescope is predicted to reveal more distant and retrograde TNOs.

Susanne Pfalzner, Amith Govind, Simon Portegies Zwart