Capture of Trojans by Jumping Jupiter

TL;DR

This study proposes a new model where Jupiter Trojans are captured during the early planetary instability, successfully matching their orbital distribution, mass, and asymmetry, and estimating the original planetesimal disk properties.

Contribution

The paper introduces the jump capture model, demonstrating its ability to reproduce Trojan characteristics and providing estimates for the original planetesimal disk mass and population.

Findings

Reproduces the orbital distribution of Trojans.

Estimates the original planetesimal disk contained 3-4×10^7 bodies.

Disk mass inferred is 14-28 Earth masses.

Abstract

Jupiter Trojans are thought to be survivors of a much larger population of planetesimals that existed in the planetary region when planets formed. They can provide important constraints on the mass and properties of the planetesimal disk, and its dispersal during planet migration. Here we tested a possibility that the Trojans were captured during the early dynamical instability among the outer planets (aka the Nice model), when the semimajor axis of Jupiter was changing as a result of scattering encounters with an ice giant. The capture occurs in this model when Jupiter's orbit and its Lagrange points become radially displaced in a scattering event and fall into a region populated by planetesimals (that previously evolved from their natal transplanetary disk to ~5 AU during the instability). Our numerical simulations of the new capture model, hereafter jump capture, satisfactorily reproduce the orbital distribution of the Trojans and their total mass. The jump capture is potentially capable of explaining the observed asymmetry in the number of leading and trailing Trojans. We find that the capture probability is (6-8)x10^-7 for each particle in the original transplanetary disk, implying that the disk contained (3-4)x10^7 planetesimals with absolute magnitude H<9 (corresponding to diameter D=80 km for a 7% albedo). The disk mass inferred from this work, M_disk=14-28 M_Earth, is consistent with the mass deduced from recent dynamical simulations of the planetary instability.