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March 15 (4:00PM) in the 2nd Floor Conference Room in Dearborn Speaker: Mario Juric (Institute for Advanced Study, Princeton) “The Eccentricity Distribution of Extrasolar Planets - Evidence of a Violent History?” The study of the origins of planetary systems has been revolutionized in the last decade by the discovery of over 200 extrasolar planets. These have vastly broadened our appreciation of the diversity of possible planetary systems, and raised a number of challenges for theories of planet formation. One of the most important is the problem of large eccentricities, for which there is no commonly accepted theory as to when and how in the course of planet formation have they arisen. The process of planetary system formation is notoriously difficult to study. An oversimplified but useful approach is to divide it into two stages, based on the importance of the effects of gas and the protoplanetary disk on the growing planets. Stage 1 lasts a few Myr, until the dissipation of the gaseous protoplanetary disk, with Stage 2 lasting from the end of Stage 1 until the present. In this talk, I will describe the results of exploration of dynamical effects of Stage 2 evolution through long-term numerical integrations of large ensembles of randomly constructed planetary systems. Most interestingly, we find the eccentricity distributions of dynamically active ensembles relax towards a common final distribution which agrees well with the one observed in extrasolar planets (excluding the tidally circularized hot Jupiters). These simulations also reproduce or predict a number of other observationally accessable properties, which I will discuss. If this mechanism truly is the source of high eccentricities, it follows that planetary systems must be formed in crowded and dynamically unstable configurations. |