Planetary Spin and Obliquity from Mergers

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 $S$ and obliquity ${\Theta }_{\mathrm{SL}}$ of the merger products have simple analytical forms: $f_S\propto S$ and $f_{\cos {\Theta }_{\mathrm{SL}}}\propto (1-{\cos }^2{\Theta }_{\mathrm{SL}}{)}^{-1/2}$. Though parameter studies, we determine the regime of validity for the analytical distributions of spin and obliquity. Since planetary mergers is 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.

References in corpus (6)

• The NumPy array: a structure for efficient numerical computation
• Dynamical Outcomes of Planet-Planet Scattering
• Origins of Eccentric Extrasolar Planets: Testing the Planet-Planet Scattering Model
• The fast spin-rotation of a young extrasolar planet
• Excitation of Planetary Obliquities Through Planet-Disk Interactions
• Breaking the centrifugal barrier to giant planet contraction by magnetic disc braking

Cited by in corpus (4)

• Heavy-metal Jupiters by major mergers: metallicity vs. mass for giant planets
• Dynamics of Colombo's Top: Tidal Dissipation and Resonance Capture, With Applications to Oblique Super-Earths, Ultra-Short-Period Planets and Inspiraling Hot Jupiters
• Constraining the oblateness of transiting planets with photometry and spectroscopy
• Future destabilisation of Titan as a result of Saturn's tilting