Oort cloud is 10—100x more massive than theory would predict!
- Planetesimal driven planet migration.
- The giant planets migrate when embedded in a disk. (Fernandez & Ip)
- Neptune goes outward because it is easier to feed things to Uranus than to kick them out.
- The Kuiper belt resonant population was due to this. (Malhotra 1995)
- Two types:
- Smooth migration. (Malhotra 1995; Hahn & Malhotra)
- Violent migration (Thommes, Duncan, & Levison 1999)
- Which includes the so-called Nice model.
- Can be no more than 40 Earth-masses in the disk or planets move too far.
- Oort cloud formation is 5% efficient cloud < 2 Earth-masses.
- Observations say it is between 4 and 80 Earth-masses.
- Oort cloud / scattered disk ratio.
- Long-period comets come from Oort cloud OC contains ~4x1011. (Francis 2008)
- Jupiter-family comets come from SD SD contains ~2x108. (Duncan & Levison 1997)
- OC formation models say the ratio should be 10:1 SD should contain ~4x1010.