core040.html

The Time-Scale Problem

The cores of Jupiter and Saturn have to form bafore the gas goes away.
- Disks last 3-5 Myr. (Earth took between 50 and 100Myr to form!)
This can only happen if system is cold.
- Recall
- However, the embryos want v_esc/v_rel~1.
- Need some damping to keep v_rel small.
  - This damping as traditionally been assumed to the result of aerodynamic drag.
Problem: Aerodynamic drag leads to radial migration and thus planetesimal depletion
............... (Thommes et al.; Inaba & Wetheril).
- At least a ~10X MMSN is required to get this to work (Thommes et al. 2003).
- Fragmentation will make things worse! (Inaba & Wetheril)