PF-07-0012

Formation of a wide-orbit giant planet in gravitationally unstable subsolar-metallicity protoplanetary disks

Ryoki Matsukoba, Eduard I. Vorobyov, Takashi Hosokawa

Direct imaging observations of planets revealed that wide-orbit (> 10 au) giant planets exist even around low-metallicity host stars and do not require metal-rich environments for their formation. A possible formation mechanism of wide-orbit giant planets in low-metallicity environments is the fragmentation of gravitationally unstable protoplanetary disks. Here, we follow the evolution of the disk for 1 Myr after its formation by way of two-dimensional hydrodynamical simulation and examine the planet formation via the disk fragmentation. We find a planet that survives till the end of the simulation. The planet is formed by the merger of two fragments at ~0.5 Myr elapsed from the disk formation, and then it orbits ~200 au from the host star for ~0.5 Myr. The planet mass is 10 Jupiter mass at its birth and gradually decreases to 1 Jupiter mass because of the tidal effect from the host star. Therefore, our results indicate that the disk fragmentation is a promising pathway to form wide-orbit giant planets. We also find the fragmentation of the circumplanetary disk. Although no fragment survives in the circumplanetary disk in our simulation, that phenomenon may help to form satellites.