Protoplanetary Propellers in Perturbed Accretion Disks.

• Applicant: Professor Frank Spahn, Ph.D.
• Subject Area: Astrophysics and Astronomy
• Term: from 2009 to 2016
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 156182056

In this research project we want to extend our scattering-diffusion model, suitable for moonlets in planetary rings, to growing planetary embryos in preplanetary disks. Despite their large differences planetary rings and preplanetary disks share a few essential physical processes justifying this approach and providing the base for this project.Since the detection of extrasolar planets in the middle of the 90ties theories of planet formation have gained a renaissance. The detection of Jovian-like planets very close to the central star has initiated investigations of disk-planet interactions and related migration of protoplanets. Two classes of migrating planets are distinguished: laige gap-inducing planets, and alternatively, small protoplanets unable to clear a gap in the disk.These classes remind closely of moonlets in planetary rings - such as Saturn s Pan and Daphnis creating an empty gap or those carving propeller-like structures in planetary rings as predicted by our models. And indeed, the cameras on the Cassini spacecraft caught a few hundred propellers caused by moonlets with sizes of 50 ... 150 meters! Moreover, a very large propeller pointing to a kilometer-sized moonlet has been found which migrates stochastically.The obvious analogies in both disks provoke the questions: Do non-gap opening planets induce propeller-like structures in preplanetary disks? Under which conditions? Do these planets cause observable modifications of the vertical disk-stratification? What processes can break the symmetry of the propeller-like structures to cause planetary migration? What is the effect of an accreting planetary embryo on the surrounding disk-structure?And finally, the very fact of a migrating moonlet in Saturn s rings provides an ultimate proof for planetary rings being a natural dynamical lab for cosmic disks and also supports the possible importance of an extended scattering-diffusion model for planet formation/migration.

• DFG Programme: Research Grants
• Participating Person: Professor Dr. Carsten Henkel