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Other Solar Systems (cont)

Radial velocity searches have only found planets about ~5% of stars.
They would not have found our solar system.
- Jupiter's orbital period is too long.
Copernican Cosmological Principle: we are not at a special place.
Antropic Principle: we are at a special place.
So, we have no idea what a typical solar system looks like!

Build solar systems on the computer and try to find out!

So, how do planets form?

Disk of gas and dust forms.
- Gas evaporates before all the planets form.
1-10km objects form by two-body accretion.
- Two phases:
  1. Local accretion (good analytic models).
  2. Global accretion (no good analytic models).
- Inner solar system is warm terrestrial planets.
- Outer solar system is cold Ice giants and cores of gas giants.
If objects get large enough (M ~ 15 ) before gas disk goes away
- Ice giants gas giants.