The Solar Nebula Theory
Two ways of building planets
- Larger planetesimals attract smaller ones. They collide and merge to make a bigger planetesimals. These attract more and eventually form the planets
- Near the sun, the nebular hydrogen gas is too hot (moving to fast) to form an atmosphere around the planets. Distant planets begin to form hydrogen atmospheres once they get big enough.
- The Jovian planets captured their atmospheres.
As time goes on the nebula cools, making the “frost line” move inward.