Mass Growth and Evolution of Giant Planets on Resonant Orbits

A pair of giant planets that tidally interact with a gaseous disk may undergo convergent orbital migration and become locked into a mean motion resonance (MMR). If the planet masses are similar to those of Jupiter and Saturn, typical after-formation conditions in protoplanetary disks lead to capture in the 2:1 MMR. Larger gas densities may cause capture in the 3:2 MMR instead. Here we present the results of hydrodynamical models of the evolution of a pair of planets, initially locked in the 2:1 or 3:2 MMR, as they interact with each other and the disk. We focus on the issue of ongoing gas accretion, the importance of which depends on the local disk mass. The high density required for capture in the 3:2 MMR causes a rapid change of the masses and mass ratio. Ensuing planet-planet interactions raises both orbital eccentricities and leads to scattering episodes and to the ejection of one of the planets from the system. Conditions compatible with 2:1 MMR locking can also lead to a more or less substantial growth of the planet masses, depending on the disk density. However, for planets orbiting in the 1 AU region, the resonant configuration appears stable up to masses of about 5 Jupiter's masses. Support from NASA Outer Planets Research Program and NASA Origins of Solar Systems Program is gratefully acknowledged.