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H. Levison, L. Dones (SwRI), M. Duncan (Queen's U.), P. Weissman (JPL)
We are in the process of completing a detailed model of the formation of the Oort cloud. We integrated the orbits of ~1800 test particles, initially in low-inclination, nearly-circular orbits between the giant planets for times up to four billion years. This simulation included the gravitational effects of the Sun, four giant planets (in their current configuration), galactic tides, and passing stars. The trajectory of a particle was followed until it was ejected from the solar system, or impacted the Sun or a planet. We find that all regions of the proto-planetary disk contribute to the Oort cloud. The Oort cloud was built in two distinct stages in our models. In the first 5 \times 107 years, the Oort cloud was built by Jupiter and Saturn. These planets delivered particles initially from all regions of the proto-planetary disk directly to semi-major axes between 10,000 and 100,000 AU. After this time, the Oort cloud was built mainly by Neptune. Objects that entered the Oort cloud during this time also came from all regions of the proto-planetary disk, but spent some time in the scattered disk.
The author(s) of this abstract have provided an email address for comments about the abstract: hal@gort.boulder.swri.edu