Orbital Perturbations of the Galilean Satellites During Planetary Encounters

Abstract

The Nice model of the dynamical instability and migration of the giant planets can explain many properties of the present Solar System, and can be used to constrain its early architecture. In the jumping-Jupiter version of the Nice model, required from the terrestrial planet constraint and dynamical structure of the asteroid belt, Jupiter has encounters with an ice giant. Here we study the survival of the Galilean satellites in the jumping-Jupiter model. This is an important concern because the ice-giant encounters, if deep enough, could dynamically perturb the orbits of the Galilean satellites, and lead to implausible results. We performed numerical integrations where we tracked the effect of planetary encounters on the Galilean moons. We considered three instability cases from Nesvorný & Morbidelli (2012) that differed in the number and distribution of encounters. We found that in one case, where the number of close encounters was relatively small, the Galilean satellite orbits were not significantly affected. In the other two, the orbital eccentricities of all moons were excited by encounters, Callisto's semimajor axis changed, and, in a large fraction -2of trials, the Laplace resonance of the inner three moons was disrupted. The subsequent evolution by tides damps eccentricities and can recapture the moons in the Laplace resonance. A more important constraint is represented by the orbital inclinations of the moons, which can be excited during the encounters and not appreciably damped by tides. We find that one instability case taken from Nesvorný & Morbidelli (2012) clearly fails this constraint. This shows how the regular satellites of Jupiter can be used to set limits on the properties of encounters in the jumping-Jupiter model, and help us to better understand how the early Solar System evolved.

The Origin of Neptune’s Unusual Satellites from a Planetary Encounter

“…As expected (cf. Deienno et al 2014), they are mostly near-parabolic due to strong gravitational focusing. The resemblance of the distribution of i enc (measured in the Neptunian-centric frame, see below) to a sine function suggests that the encounters are nearly uniformly distributed in the solid angle.…”

Excitation of a Primordial Cold Asteroid Belt as an Outcome of Planetary Instability

“…Finally, it is also important to discuss three other aspects: (i) as the instability depicted in this work requires a relatively long sequence of Jupiter's jumps, it is important to check that a long phase of close encounters between Jupiter and pl5 does not destabilize the regular satellite system of Jupiter . Deienno et al (2014) concluded that what is important for the stability of the satellites is not the total number of encounters, but the distance of the closet one. Following Deienno et al (2014), the orbits of the Galilean satellites can be profoundly affected if the encounter distance (d enc ) between Jupiter and pl5 is d enc < 0.03 au.…”

“…Deienno et al (2014) concluded that what is important for the stability of the satellites is not the total number of encounters, but the distance of the closet one. Following Deienno et al (2014), the orbits of the Galilean satellites can be profoundly affected if the encounter distance (d enc ) between Jupiter and pl5 is d enc < 0.03 au. They found that, 0.03 au < d enc < 0.05 au causes only small perfectly the constrains imposed and well representing Jupiter's current inclination.…”

Detecting and Characterizing Exomoons and Exorings

“…The orbital alignment of the Uranian moon systems suggests a "collisional tilting scenario" (Morbidelli et al 2012) and implies significant bombardment of the young Uranus. A combination of these observations constrains the migration of the giant planets (Deienno et al 2011), planet-planet encounters (Deienno et al 2014), bombardment histories (Levison et al 2001), and the properties of the early circumsolar disk (Jacobson and Morbidelli 2014). The Pluto-Charon system can be considered a planetary binary rather than a planet-moon system, since its center of mass is outside the radius of the primary, at about 1.7 Pluto radii.…”