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
stabilization? (Weidenschilling)
- If the dust/gas was ~3X solar, this would still work. (Sekiya; Youdin & Shu)
- Particle-Trapping in Eddies (Cuzzi et al.; Barranco & Marcus; Johansen et al.)
- Eddies are generated in in Solar Nebula (scales and reasons differ between papers).
- Particles settle due to gas drag
high density, low velocities
........... planetesimals
