Expert: Philip Stahl - 10/19/2008

Question
What is the main chemical composition of dust particles in
protoplanetary discs; are these particles cristalline and
do they have electrostatical charge?  

Answer
Hello,

First, the evolution of these proto-planetary disks is still not fully nailed down, so please understand the information is tentative. As we get more data and imagery from diverse sources, e.g. the Hubble Space Telescope, we can obtain more definitive answers.

In general, however, we'd expect the main chemical composition of such disks to be comprised of silicates, carbon compounds, ice and iron sulfide. From this list you can infer not all particles would be crystalline, perhaps only some of the silicates.

As for electrostatic charge, since electric (E-) fields permeate space, we would expect charge to build up anyplace wherein a solar wind or plasma (containing electric charges) flows. And this would certainly be in the vicinity of such disks. `

Indeed, one can say this presence is indispensable, since modern theory assumes that electrostatic attraction figures prominently - along with graviational attraction- in terms of accreting the dust and ice to form the disk.