Stability of Jovian Trojans and their collisional families

Abstract

The Jovian Trojans are two swarms of objects located around the L4 and L5 Lagrange points. The population is thought to have been captured by Jupiter during the Solar system’s youth. Within the swarms, six collisional families have been identified in previous work, with four in the L4 swarm, and two in the L5. Our aim is to investigate the stability of the two Trojan swarms, with a particular focus on these collisional families. We find that the members of Trojan swarms escape the population at a linear rate, with the primordial L4 (23.35 per cent escape) and L5 (24.89 per cent escape) population sizes likely 1.31 and 1.35 times larger than today. Given that the escape rates were approximately equal between the two Trojan swarms, our results do not explain the observed asymmetry between the two groups, suggesting that the numerical differences are primordial in nature, supporting previous studies. Upon leaving the Trojan population, the escaped objects move on to orbits that resemble those of the Centaur and short-period comet populations. Within the Trojan collisional families, the 1996 RJ and 2001 UV209 families are found to be dynamically stable over the lifetime of the Solar system, whilst the Hektor, Arkesilos and Ennomos families exhibit various degrees of instability. The larger Eurybates family shows 18.81 per cent of simulated members escaping the Trojan population. Unlike the L4 swarm, the escape rate from the Eurybates family is found to increase as a function of time, allowing an age estimation of approximately 1.045 ± 0.364 × 109 yr.

Metal pollution of the solar white dwarf by solar system small bodies

“…The fraction of survivors for each small body population and for different T ML is shown in Figure 2. Overall, while the MBAs and TNOs are mostly stable with no more than a few per cent lost, 40% of the JTAs are removed during the ML phase; and we confirm that JTAs in the leading L4 cloud are more resistant by a few per cent than the trailing L5 cloud, in agreement with Di Sisto et al (2014); Holt et al (2020) (this phenomenon is also observed during the WD phase). Also, in the three simulations with different T ML and most apparently for the JTAs, it seems that when time is measured against the respective T ML , the small objects tend to be lost at the same time, i.e., when the planet-star mass ratio attains some certain value.…”

“…Those objects are slowly diffusing, transversing various resonances and increasing eccentricity and inclination, causing close encounters with Jupiter and escape from the Trojan region (Robutel & Gabern 2006;Di Sisto et al 2019). The escape fraction from the L5 swarm is somewhat higher than that from L4 (Di Sisto et al 2014;Holt et al 2020). Lying in the immediate vicinity of Jupiter, the chance of collisions between the escaped JTAs with that planet becomes non-negligible, almost as frequent as that of reaching the WD Roche radius (Di Sisto et al 2019).…”

“…They have been captured by Jupiter during its early orbital migration (Nesvorný et al 2013;Pirani et al 2019). Those objects are slowly diffusing and leaking from the trojan region and perhaps ∼ 20% have been lost over the age of the solar system (e.g., Tsiganis et al 2005;Di Sisto et al 2014;Holt et al 2020). The escapees wander around in the solar system typically for a few Myr and a few per cent collide with the Sun (Di Sisto et al 2019).…”

Apsidal asymmetric-alignment of Jupiter Trojans

“…This is not unexpected since the dynamics around the L5 point is a mirror image of the L4 point in the restricted three-body problem. Furthermore, as noted in Section 1 and some other previous works (Nesvorný & Dones 2002;Di Sisto et al 2014;Holt et al 2020), under the gravitational effects of the four outer planets, the L4 and L5 Trojan swarms show almost the identical dynamical structure and stability in the long-term evolution. We thereby will only consider the L4 Jupiter Trojans in the following sections.…”

“…In this section, we still adopt the present outer solar system model, consisting of the Sun and four giant planets (i.e., Jupiter, Saturn, Uranus and Neptune). As in recent dynamical explorations of the Jupiter Trojans (e.g., Hellmich et al (2019), Holt et al (2020)), to construct robust simulations, we follow the long-term evolution of 30,000 test Trojans around the L4 point. Initially, all particles have the same semimajor axis (a ≈ 5.2 AU) with Jupiter.…”