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

In a recent paper we proposed that the giant planets' primordial orbits may have been eccentric (e(J) similar to e(S) similar to 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 planets' ultimate eccentricities, our work uncovers several intriguing outcomes in realizations where Jupiter and Saturn are born with extremely large eccentricities (e(J) similar or equal to 0.10; e(S) similar or equal to 0.25). 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.

Automated summary

Researchers propose that the giant planets' primordial orbits may have been eccentric and find intriguing outcomes in simulations where Jupiter and Saturn are born with extremely large eccentricities. Successful simulations show that the planets' orbits damp through interactions with the planetesimal disk prior to instability, suggesting a wider range of plausible evolutionary pathways for replicating the modern orbital architecture of Jupiter and Saturn.