Weidenschilling continues to investigate a number of topics related to the formation of the solar system and extrasolar planetary systems. He is developing an improved numerical model for the structure of a particle layer in the midplane of the primordial solar nebula, which can treat interacting populations of particles with different sizes. He is also using the PSI multi-zone accretion code (including a new version developed by collaborator F. Marzari, which integrates orbits of large bodies directly) to model the growth of planets in the inner and outer parts of the solar system. A new finding is that planetary embryos in the outer region are more effective at stirring the orbits of smaller bodies. This slows their growth and makes the accretion of planetary cores more difficult at larger heliocentric distances.
Another ongoing project is the evolution of small dust grains in circumstellar debris disks, such as our own asteroid belt and more massive disks observed by the Spitzer and Hubble space telescopes. Grains are produced by collisional destruction of larger parent bodies, and removed by mutual collisions, radiation pressure, and Poynting- Robertson drag due to light from the central star. Weidenschilling is adapting the collisional code to include radiative forces, and developing a hierarchical method to model dust evolution in systems containing particles ranging in size from micron-sized grains to giant planets.
S. Weidenschilling; Collisional evolution of a massive planetesimal disk during slow migration of the outer planets. 38th Lunar & Planetary Science Conference, Abstract #2107.
S. Kortenkamp, S. Weidenschilling, F. Marzari; Modeling planetesimal accretion in protoplanetary disks perturbed by massive companions. 38th Lunar & Planetary Science Conference, Abstract #2283.
A. Morbidelli, W. Bottke, J. Chambers, J. Cuzzi, S. Weidenschilling; Accretion and dynamical evolution of asteroids and comets. Workshop on the Chronology of Meteorites and the Early solar system, Abstract #4003.
Weidenschilling, S. J. (2007) Accretion of planetary embryos in the inner and outer solar system. Physica Scripta, in press (Proceedings, Nobel Symposium 135).