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A.H. Abdelhadi, D.D. Clayton (Clemson University)
Scattering of stellar orbits by galactic molecular clouds is studied in hope of explaining isotopic peculiarities of presolar grains from AGB stars. Silicon isotopic anomalies found in the mainstream SiC grains are observed to have heavy isotopes enriched. To explain the isotopic heaviness we propose that AGB stars that formed in the interior region of the galaxy, with metallically higher than solar, change their orbits during close encounters with molecular clouds. The AGB stars give up their SiC grains in winds deposited in the solar neighborhood prior to the birth of the sun. We model the dynamics by superposing on a standard axisymmetric galactic potential the discrete potentials of thousands of molecular clouds moving on constant circular orbits. Their initial positions were randomly distributed within the molecular-cloud ring. Gravity assist occurs when a star scattered into a crossing orbit by one cloud experiences forward scattering from a second cloud. We record their final positions at the AGB lifetime. Early tests show that such possibility is feasible and could have happened.
This work is supported by NASA Origin of Solar Systems Program.
The author(s) of this abstract have provided an email address for comments about the abstract: aabdelh@hubcap.clemson.edu