2026/07/04 by Yuhito Shibaike, Satoshi Okuzumi, Takahiro Ueda +2
Physics and Astronomy · #Astrophysics and Star Formation Studies #Stellar, planetary, and galactic studies #Astro and Planetary Science
paper · pdf · doi:10.3847/2041-8213/ae86f5
Abstract Giant planets form small gas disks, called circumplanetary disks (CPDs), during gas accretion. The CPD of PDS 70 c has been detected by the Atacama Large Millimeter/submillimeter Array in (sub)millimeter continuum emission, which is interpreted as thermal emission from dust in the CPD. The resulting spectral index suggests that the disk is optically thick over a wide range of wavelengths. However, this is inconsistent with previous CPD dust models, which predict that the disk is optically thin because of radial dust drift. Here, we present a new interpretation of the multiwavelength observations: the CPD hosts an optically thick dust ring, whose existence has been discussed in the context of satellite formation. We demonstrate that a dust-ring model that incorporates gas accretion, dust evolution, and dust thermal emission is consistent with the observations under reasonable conditions, whereas a conventional ringless model requires more stringent conditions. We also show that the dust ring inferred from the observations potentially satisfies the conditions for exomoon formation via streaming instability and subsequent gravitational instability.