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THE MIGRATION OF GAS GIANT PLANETS IN GRAVITATIONALLY UNSTABLE DISKS

Planets form in the disks of gas and dust that surround young stars. It is not known whether or not gas giant planets on wide orbits form the same way as Jupiter or form by the fragmentation of gravitationally unstable disks. Here we show that a giant planet that has formed in the outer regions of a protostellar disk initially migrates quickly toward the central star (migration timescale ∼ 10 4 ?> years) while accreting gas from the disk. However, in contrast with previous studies, we find that the planet eventually opens up a gap in the disk and the migration is essentially halted. At the same time, accretion-powered radiative feedback from the planet significantly limits its mass growth, keeping it within the planetary-mass regime, (i.e., below the deuterium burning limit) at least for the initial stages of disk evolution. Giant planets may therefore be able to survive on wide orbits despite their initial fast inward migration, consequently shaping the environment in which terrestrial planets that may harbor life can form.