Highly inclined and eccentric massive planets

Abstract

Context. Observational evidence indicates that the orbits of extrasolar planets are more various than the circular and coplanar ones of the Solar system. Planet-planet interactions during migration in the protoplanetary disc have been invoked to explain the formation of these eccentric and inclined orbits. However, our companion paper (Paper I) on the planet-disc interactions of highly inclined and eccentric massive planets has shown that the damping induced by the disc is significant for a massive planet, leading the planet back to the midplane with its eccentricity possibly increasing over time. Aims. We aim to investigate the influence of the eccentricity and inclination damping due to planet-disc interactions on the final configurations of the systems, generalizing previous studies on the combined action of the gas disc and planet-planet scattering during the disc phase. Methods. Instead of the simplistic K-prescription, our n-body simulations adopt the damping formulae for eccentricity and inclination provided by the hydrodynamical simulations of our companion paper. We follow the orbital evolution of 11000 numerical experiments of three giant planets in the late stage of the gas disc, exploring different initial configurations, planetary mass ratios and disc masses. Results. The dynamical evolutions of the planetary systems are studied along the simulations, with a particular emphasis on the resonance captures and inclination-growth mechanisms. Most of the systems are found with small inclinations (≤ 10• ) at the dispersal of the disc. Even though many systems enter an inclination-type resonance during the migration, the disc usually damps the inclinations on a short timescale. Although the majority of the multiple systems in our simulations are quasi-coplanar, ∼ 5% of them end up with high mutual inclinations (≥ 10• ). Half of these highly mutually inclined systems result from two-or three-body mean-motion resonance captures, the other half being produced by orbital instability and/or planet-planet scattering. When considering the long-term evolution over 100 Myr, destabilization of the resonant systems is common, and the percentage of highly mutually inclined systems still evolving in resonance drops to 30%. Finally, the parameters of the final system configurations are in very good agreement with the semi-major axis and eccentricity distributions in the observations, showing that planet-planet interactions during the disc phase could have played an important role in sculpting planetary systems.

Formation of planetary systems by pebble accretion and migration: growth of gas giants

“…In both observed systems two gas giant planets recide on similar orbital configurations, including eccentricities exceeding 0.3. This type of evolution is comparable to previous simulations of planetplanet scattering (Marzari & Weidenschilling 2002;Chatterjee et al 2008;Jurić & Tremaine 2008;Sotiriadis et al 2017).…”

“…with K damp = 100, where typically K damp = 1 − 100 (Lee & Peale 2002). Using these short damping time-scales, Sotiriadis et al (2017) showed that migration and scattering events of giant planets during the gas phase can reproduce the eccentricity distribution of giant planets. Previous works, using different giant planet damping time-scales, have concluded similarly (Jurić & Tremaine 2008;Moeckel et al 2008;Matsumura et al 2009).…”

Are the observed gaps in protoplanetary discs caused by growing planets?

“…These simulations clearly predict a large population of giant planets that could be seen by direct imaging surveys, for example, the HR8799 system, but rarely by the RV method. The observed gas giants in reality are mainly on eccentric orbits, therefore they most likely underwent gravitational scattering (Jurić & Tremaine 2008;Sotiriadis et al 2017). This means the large population of synthesised giant planets in the direct imaging field of view could be scattered by gravitational interaction which might refill the dearth of the planets in the RV field of view should N-body interaction between the protoplanets been incorporated.…”

Torques on Low-mass Bodies in Retrograde Orbit in Gaseous Disks

“…In the standard descriptions of prograde type II migration, the timescale is estimated as a first approximation by (Sotiriadis et al 2017, and references therein). However, more detailed simulations have demonstrated that the type II migration timescale in the prograde case can be larger or smaller than τ (p) II , depending on the disk mass (Duffell et al 2014;Dürmann & Kley 2015).…”