lec11_23oct2009

lec11_23oct2009 - Ge/Ay133 How do small dust grains grow in...

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Unformatted text preview: Ge/Ay133 How do small dust grains grow in protoplanetary disks? How do we go from a well mixed gas/dust grain disk: To a mature planetary system? For solids, it is helpful to distinguish amongst several regimes: μ m → cm → km → moon/Mars (oligarchs) → 1-10 M Earth Step #1: Growth from ~0.1 μ m to ~1 cm scales Need to think about how particles move in the sub-Keplerian field provided by the gas. First let’s look at the radial component. Drag force on particles, c = sound speed... Stopping time (shed momentum). δ = particle density, Σ gas surface density. For small particles, well coupled to gas , radial velocity is Very slow for small particles. Thus, let’s think about vertical motion at a given R: The mean free path is >> the particle diameter, so in the Epstein not Stokes regime (that is, the Brownian motion case). Thus… NO particle growth....
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  • Fall '10
  • list
  • Armitage, protoplanetary disk, small dust grains, protoplanetary nebula, critical  random speed, quiescent dust disk

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lec11_23oct2009 - Ge/Ay133 How do small dust grains grow in...

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