Planetary Spin and Obliquity from Mergers

Jiaru Li and Dong Lai

Publication: Astrophysical Journal Letters 898, L20, 2020

Abstract: In planetary systems with sufficiently small inter-planet spacing, close encounters can lead to planetary collisions/mergers or ejections. We study the spin property of the merger products of two giant planets in a statistical manner using numerical simulations and analytical modeling. Planetary collisions lead to rapidly rotating objects and a broad range of obliquities. We find that, under typical conditions for two-planet scatterings, the distributions of spin magnitude and obliquity of the merger products have simple analytical formulae. Through parameter studies, we determine the regime of validity for the analytical distributions of spin and obliquity. Since planetary mergers are a major outcome of planet-planet scatterings, observational search for the spin/obliquity signatures of exoplanets would provide important constraints on the dynamical history of planetary systems.

Paper links: [publisher] [arXiv] [NASA ADS]