Top Story #2: The Giant Planets Form
- The cores formed by 2-body accretion followed by direct gas accretion.
- So, the planets must have formed when gas disk is still around.
- Disk lifetimes are a few Myr. (Haisch et al. 2001)
- The 4 giant planets formed in mean motion resonances with one another. (Morbidelli et al.)
- Jupiter and Saturn were in the 2:3 MMR.
- Most likely reason that we do not have a hot Jupiter. (Masset & Snellgrove 2001)
- All within 12AU of the Sun!
- Core formation was not 100% efficient .. (it was 50 +/- 50%).
- Probably needed 5 — 10x MMSN to build cores fast enough.
- Most objects gravitationally scattered outward by planets:
- Formed a first generation Oort cloud at ~1000 AU.
(Eggers 99; Fernandez & Brunini 02; Brasser et al. 06; 11;
Kaib & Quinn 08)
- Sedna is probably one of these objects.
- A couple % of comets end up in this structure.
- A lot could be S- and C-type asteroids if Grand Tack is right.
(Walsh et al. 2011)
- The rest are ejected to the cluster.
(Brasser et at. 2006)