Why Mean Motion Resonances?
This is most likely initial state of giant planets.
- Planets will migrate if placed in a gas disk.
(Goldreich & Tremaine; Ward)
- Probably caused the hot Jupiters.
- Why did this not happen here?
- Migration stops if Jupiter and Saturn are in the 2:3MMR.
Masset & Snellgrove (2001)
- Which is MUCH closer than they are today.
- Uranus and Neptune placed in this system will migrate until they are in MMRs.
- Four configurations are stable after the gas goes away.
- Indeed, many extra-solar planetary systems are in MMRs.
(Pawel Artymowicz) ......