The 41/2 Steps of Terrestrial Planet Formation in the Solar System.
Step 0.5: Once the the disk forms the dust settles to a the mid-plane.
Step I: A miracle occurs, Planetesimal Formation (i.e. 1-10km objects form)
- Standard two-body accretion forms planetesimals.
- Particles spiral into the Sun?
- How do you get two rocks to stick?
- Gravitational instability (Goldreich & Ward).
- As dust layer settles, dust disk becomes unstable planetesimals.
- But, dust will orbit faster than gas turbulence
- Particle-Trapping in Eddies (Cuzzi et al.)
- Large-scale eddies in Solar Nebula.
- Particles settle due to gas drag
high density, low velocities