Project P1: Masses and stirring of debris disks (AIU/Jena)


The main goal of this project is to develop a detailed understanding of the origins of debris disks and determine how exactly the dust we see is related to the planetesimals that we do not see. This includes addressing the mass budget and stirring mechanisms. Our studies in the first phase uncovered the “disk mass problem”: the total mass of bright disks required to reproduce them with collisional models is much higher than the mass of solids in the preceding protoplanetary phase. We will investigate several possibilities to resolve this controversy. Another key question is what excites planetesimals in debris disks and when, activating dust production. In the first phase, we found that self-stirring by mid-sized planetesimals is more efficient than thought previously. Yet the efficiency critically depends on the total disk mass, i.e., is related to the disk mass problem. Also, if for some reasons the stirring is delayed, this might mitigate the requirement of high mass. We will develop detailed models of self-stirring. We will also consider a possibility of “indirect planet stirring”, in which planets create a scattered disk component of the disk, which then stirs the dynamically cold one. In our modeling, we will assume a “pebble-pile” structure of planetesimals, as predicted by state-of-the-art planetesimal formation models, and benefit from collaboration from projects P5−P8 that probe collisional and compositional properties of pebble-pile analogs.