Moonlets in planetaren Ringen: Implikationen für die Ringteilchendynamik?

• Applicant: Professor Frank Spahn, Ph.D.
• Subject Area: Astrophysics and Astronomy
• Term: from 2010 to 2014
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 164011225

The prediction of propeller structures in Satum s rings caused by embedded small satellites (moonlets) by Spahn and Sremcevic (2000), Sremcevic et al. (2002) and Seiß et al. (2005) led to recent detections of moonlets in Saturn s rings (Tiscareno et al., 2006; Sremcevic et al., 2007; Tiscareno et al., 2008). The brightness of the propeller structures, however, deviated from the formerly predicted features. A preliminary photometric study of particle configurations obtained from N-body simulations demonstrated that the brightness of the propeller pattern can in principle be understood if small debris particles are produced in perturbed regions (Sremcevic et al., 2007). This debris, formerly resting on the surfaces of larger ring particles, can be released due to enhanced impact velocities in perturbed ring regions, in this way increasing the brightness of the observed propeller features. The aim of the project is to calculate the change of the particles size distribution of an ensemble of adhering and gravitating ring particles due to perturbations. The resulting modifications of the optical depth will then be determined and related to the observed propellers. In this way an improved understanding of the dependence of the observed pattern in the ring brightness on the underlying perturbation in the mass density can be obtained. This will in turn lead to improved constraints for the mass of the embedded moonlets, the ring viscosity as well as an estimate for the strength of the adhesion between the ring particles and its importance for the ring particle size distribution. A model for the change of the size distribution in perturbed ring regions could also be applied to other ring features as the missing ring brightness asymmetry effect in the outermost A ring, the brightness halos around strong resonances (e.g. Janus 5:4 density wave, Nicholson et al. (2008)) and the temporary clumps and brightness bursts in Saturn s F ring.

• DFG Programme: Research Grants