Freiburg 2008 – wissenschaftliches Programm
Bereiche | Tage | Auswahl | Suche | Downloads | Hilfe
EP: Fachverband Extraterrestrische Physik
EP 10: Planets and Small Bodies II
EP 10.1: Hauptvortrag
Mittwoch, 5. März 2008, 16:45–17:15, KGI-Aula
A moonlet belt in Saturns ring — •Frank Spahn1, Miodrag Sremcevic2, Juergen Schmidt1, Martin Seiss1, Heikki Salo3, and Nicole Albers2 — 1Universitaet Potsdam, Potsdam, Deutschland — 2LASP, Univ. Boulder at Colorado, U.S.A. — 3Univ. Oulu, Oulu, Finland
We investigate the action of small ring-moons in Saturn's rings. The analytical model includes viscous diffusion of the disc matter and gravitational scattering by the moonlet as counteracting processes. Two types of density structures are found, depending on the mass of the moonlet and on the momentum transport in the ring. A gap around the whole circumference of the disc is opened if an icy ring-moon were larger than one kilometre in size. Alternatively, a local S-shaped density modulation is generated by smaller moonlets -- structures that we called a "propeller".
These results have been checked by inspections of the Cassini-imaging data which revealed 12 "propellers" in the 100-metres size range to reside in Saturn's A ring up to date. From these observations we estimate a few million of 100m moonlets populating a narrow annulus of about 3000 km width in the middle of the A ring. This finding is of crucial importance for the origin of the rings.
Our studies may be of relevance for discs around a protostar with a protoplanet embedded. Again either gaps or "propellers" can be expected to have formed within the disk. Future telescopes might offer the chance to be witness of a planetary growth by studying such structures in circum-stellar disks.