Born extra-eccentric: A broad spectrum of primordial configurations of the gas giants that match their present-day orbits

TL;DR

This study explores a broad range of primordial gas giant configurations, showing that even highly eccentric initial orbits can evolve into the current orbital architecture through planetesimal interactions and dynamical instabilities.

Contribution

The paper provides comprehensive simulations demonstrating that primordial gas giant orbits with high eccentricities can lead to present-day orbits, expanding the range of plausible planetary evolution scenarios.

Findings

High initial eccentricities for Jupiter and Saturn are possible and can evolve into current orbits.

Planetesimal disk interactions damp planetary eccentricities before instability occurs.

A wider range of primordial configurations can produce the observed orbital architecture.

Abstract

In a recent paper we proposed that the giant planets' primordial orbits may have been eccentric (~0.05), and used a suite of dynamical simulations to show outcomes of the giant planet instability that are consistent with their present-day orbits. In this follow-up investigation, we present more comprehensive simulations incorporating superior particle resolution, longer integration times, and eliminating our prior means of artificially forcing instabilities to occur at specified times by shifting a planets' position in its orbit. While we find that the residual phase of planetary migration only minimally alters the the planets' ultimate eccentricities, our work uncovers several intriguing outcomes in realizations where Jupiter and Saturn are born with extremely large eccentricities (~0.10 and ~0.25, respectively). In successful simulations, the planets' orbits damp through interactions with the planetesimal disk prior to the instability, thus loosely replicating the initial conditions considered in our previous work. Our results therefore suggest an even wider range of plausible evolutionary pathways are capable of replicating Jupiter and Saturn's modern orbital architecture.