Interpreting Debris Disks

Detailed theoretical modelling is required to make an accurate interpretation of the observed images.

First of all modelling is required to deconvolve the underlying morphology of the structure in the images. For example, modelling showed that a bend in the emission profile in the 450 µm image of the Fomalhaut disk is caused by a clump embedded in the dust ring (Wyatt & Dent 2002; Holland et al. 2003):

Modelling of the Fomalhaut disk also considered the origin of the dust grains. A variety of modelling techniques, ranging from interpreting the emission spectrum to considering the effect of collisions and radiation forces on the disk material, resulted in the following picture of the size distribution of material in Fomalhaut’s disk. It appears that the dust we observe is just the bottom half of a collisional cascade which starts with the destruction of km-sized planetesimals (Wyatt & Dent 2002).

Most recently, a model was developed to explain the clumpiness of these debris disks. In this model, the clumps arise because many planetesimals were trapped into the resonances of a planet when that planet’s orbit expanded early in the history of the system. Application of the model to the Vega system showed that its two asymmetric clumps can be explained by the migration of a Neptune-mass planet from 40-65 AU over a period of 56 Myr (Wyatt 2003). A similar migration has been proposed for our own Neptune in the solar system to explain the resonant structure of the Kuiper Belt. This implies that the putative planetary system toward Vega may have formed and evolved in a similar way to our own.

 

The Royal Observatory Edinburgh comprises the UK Astronomy Technology Centre of the Science and Technology Facilities Council, the Institute for Astronomy of the University of Edinburgh and the ROE Visitor Centre.