Forschergruppe FOR 759

The Formation of Planets:
The Critical First Growth Phase

Project A1

INTRODUCTION

Since the ISO (Infrared Space Observatory) mission we know that dust particles in proto planetary disks are partly crystalline and that one of the main processes leading to the crystallisation from amorphous cosmic dust is thermal annealing (e.g. Gail 2001).

In this project we want to constrain the kinetics of the crystallisation process of silicate dust particles in proto planetary disks, e.g. time scale and activation energy for nucleation and grain growth. We wish to provide reliable laboratory data for astrophysical modelling of thermal annealing of silicates in the proto planetary disk. Our special interest concerns the physico-chemical processes and the radial abundance of amorphous, respectively crystalline cosmic dust at various evolutionary stages of the disk.

Different experimental sequences, not comparable starting materials (e.g. gels and smokes) with chemical inhomogeneities and inclusions of crystal seeds led to contradictory results in previous studies (e.g. Fabian et al. 2000; Hallenbeck et al. 1998; Jäger et al. 2003; Kaito et al. 2006; Rietmeijer et al. 2002; Thompson et al. 2002). There were also vast discrepancies in the definition of the degree of crystallinity.