The Formartion of Uranus and Neptune
A Nice Pretty Picture: The Standard Model

Three major stages of planet formation:

1. 1-10km objects form by two-body accretion, gravitational instability, turbulence
   or something else.
   
   
2. Big guys grow faster than small guys run away.
   
   • ..............
   • And since .
   • As long as is not affected by big guys.
     
     
   • Assumed to end when embryo feeding zones run into one another (Lissauer 1993)
   
   
3. Big guys dynamically interact and grow via collisions. (Late-Stage)
   • Fernandez & Ip build Uranus and Neptune from Lunar/Earth-mass objects in < 2x10⁷ years.
     • Used a Monte Carlo, Öpik code.
   • Brunini & Fernandez `confirm' these results with direct N-body calculations.
   So, problem solved! ................ Right?