Clean up of small bodies which were not accreted onto protoplanets
was the last and longest stage in planet formation.
After oligarchy, protoplanets cleared wide gaps around their
shut off the accretion of small bodies from just outside their Hill
radii. Gravitational instability in the disk of small bodies produced
larger ones whose random velocities were excited until their orbits
crossed those of neighboring protoplanets. In the inner planet system,
these bodies were ultimately incorporated into planets that continued
to grow. In the the outer planet system these bodies were ejected and
either took up residence in the Oort cloud or escaped from the sun. An
important distinction between the formation of inner and outer planets
is that growth of the former continued through clean up, whereas
formation of the latter was essential complete by the end of
oligarchy. This implies that the surface density of the
proptoplanetary disk was that of the minimum solar mass nebula in the
inner planet region but about six times larger in the outer planet
region. The timescale through clean up was set by the accretion rate
at the geometrical cross section in the inner planet region, and by
the ejection rate at the gravitationally enhanced cross section in the
outer planet region. It was a few hundred million years in the former
and a few billion years in the latter.
The Oort cloud, should therefore contain as much mass in
larger than earth objects as in kilometer size bodies. Both
originate in the outer planetary region.
Begin WebCam and audio for the whole talk: high bandwidth or medium bandwidth.
Begin QuickTime of the whole talk (high bandwidth).
To begin viewing slides, click on the first slide below. (Or, view as pdf.)
Author entry (protected)