Runaway Gas Accretion
Runaway gas accretion is the accelerated accretion of gas from the protoplanetary disk onto a growing giant planet. The runaway gas accretion phase is thought to occur when the mass in a planetary core’s gaseous envelope is comparable to the core mass, and a large reservoir of gas remains in the disk. Runaway gas accretion is quenched when the planet carves an annular gap in the disk, having accreted all the gas within its direct gravitational influence, i.e., its Hill sphere. Dynamical instabilities, for example, due to interactions with the gas disk, could however increase the planetary eccentricity and restore a large accretion rate of gas, for massive enough planets.