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P.C. Frisch (Univ. Chicago)
A complete description of nearby planetary systems requires an understanding of the present and past dynamical interactions between the winds of the central star and ambient interstellar material (ISM, Frisch, 1993, ApJ v.407, p198). The 3D space motions of about 50 nearby planetary systems are calculated using recent astrometric and radial velocity data. The comparison of these motions with the distribution of nearby interstellar material (the 'Local Fluff'), along with estimates for stellar winds, permits an evaluation of the past and present interplanetary environments for these stars. Inner and outer planets have been shown to have significantly different levels of exposure to raw ISM since n~10 cm-3 clouds may contract astrospheres to within ~10 AU of the central star (depending on relative ISM/stellar wind ram pressures). The unknown strength of nearby interstellar magnetic fields poses a significant uncertainty in evaluating the confining pressure for the astrospheres of nearby stars.
The author would like to thank NASA for supporting this research.