Outward Migration of Two Planets in Resonance

Studies of planet migration due to the interaction of the planets with the parent circumstellar disk are of paramount importance to understand the evolution of the orbital elements of exoplanets. It was shown that planet migration can lead to resonance capture, during which the planets exert a regular and periodic gravitational influence on each other. Depending on the details of the resonance process, this phenomenon can either stabilize or destabilize the orbits of the involved bodies. The case of a Jupiter-Saturn system shows the occurrence of a two-stage migration, based on the coupling between planet migration due to the interaction with the gaseous disk and a 3:2 mean motion resonance. In this work it was chosen to investigate via numerical modeling the effects of the model resolution on the migration of a Jupiter-Saturn pair locked in resonance. The choice of this type of analysis follows from the results obtained by recent 2-dimensional preliminary simulations performed with the hydrodynamical code FARGO3D. It was found that by increasing the resolution of the grid firstly by a factor of 2 and subsequently by a factor of 3, the results are different compared to the low-resolution case. In the high resolution case, it seems to be the second-order 5:3 mean motion resonance to drive the outward migration of the two-planets and not the usual 3:2 commensurability. The medium resolution case shows an intermediate behaviour, with a temporary capture in the 5:3 mean motion resonance and a final arrangement in the 3:2 commensurability. The obtained results raise several questions regarding whether the observed outcomes are due to an intrinsic issue within the FARGO3D code or if the resolution of the model indeed influences the type of resonance capable of driving the outward planet migration. In order to explore further this problem, an alternative hydrodynamical code, namely PLUTO, is employed to investigate the coupled evolution of a Jupiter-Saturn pair within its parent protoplanetary disk.