So, what happened to the mass?
- Dynamical excitation: Something excited the KB feeding most of mass inward.
- Collisional Grinding: In an excited KB collisions grind it down.
But, none of these appear to work very well.
We can circumvent the mass depletion problem if:
- we imagine the planetesimal disk was truncated near 30AU (Levison & Morbidelli 2003:
) , and
- the Kuiper belt was pushed out.
The Nice Model supplies us a mechanism to doing this (and getting the orbits as well
):
- As Neptune scatters disk particles, they can be temporally trapped in resonances.
- The resonances are wider if Neptune's eccentricity is large.
- Recall that Neptune goes through a high eccentricity phase as it settles into its current orbit.
- So, the resonances start out wide and decrease with time.
- Objects can be trapped during this time.
- This process can capture the Kuiper belt that we see!
- Given our disk of 35 Earth-mass
~0.05 to 0.15 Earth-mass belt
- Observation say between ~0.01 and ~0.1 Earth-mass.
- All this predicts that the size-distribution of KB and Trojans should be the same.
- Could only show this recently.
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