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Orbital resonances and planetary accretion in the early solar system evolution

Thesis/Dissertation ·
OSTI ID:6828219
The solar system, in its early evolution, is thought to have consisted of an accretion disk around a growing central protostar. The accretion disk from which the planets ultimately formed can play a significant role in the processes of planetary and solar formation. As well as leading, by thermalization of orbital motions in the disk, to bipolar flows in the T Tauri stage of stellar evolution, the disk can influence the course of planetary accumulation. By virtue of its essentially solar composition, Jupiter was formed before the accretion disk was removed. This first-formed planet then gravitationally imposed a harmonic strucnture on the planetesimal swarm through its commensurability resonances. Accelerated growth of planetesimals in orbital resonance with Jupiter resulted in runaway growth producing planetary embryos. These embryos accelerated growth at their own resonances in a process that propagated inward and outward forming a resonant configuration of embryos. When the accretion disk is eventually dispersed, the radial force law changes so that this resonant structure of preplanetary zones is transformed into the present non-resonant structure. During this process, the strong resonances of Jupiter swept through the asteroid zone. Motion of commensurability resonances leads to a new celestial mechanical effect where eccentricities are permanently increased and semimajor axes are permanently decreased by significant amounts. The eccentricity excitation, producing collision velocities resulting in catastrophic fragmentation, can explain the lack of a planet in that region. The semimajor axis reduction can account for the clearing of the Kirkwood gaps.
Research Organization:
Texas Univ., Austin (USA)
OSTI ID:
6828219
Country of Publication:
United States
Language:
English