Joint Astrophysics Colloquium

Atmospheric Dynamics in Short-Period Extrasolar Planets

Ian Dobbs-Dixon

McGill University

Among the approximately 250 extra-solar planets discovered to date, 20% orbit their host stars with periods less then 5 days. Unlike the gas-giants in our solar system, these planets are intensely irradiated by their central star. The impinging radiation on a planet in a 3 day orbit is approximately five orders of magnitude larger then the planets internal flux, dominating the energy budget. In addition, the spin synchronization timescale is quite short. Therefore, it is widely believed that a majority of these systems are tidally locked, resulting in slow rotation and day-side temperatures of up to 2000K. Recent and ongoing transit observations in both the optical and IR have yielded a wealth of information about these objects, including structural constraints, spectra, and surface temperature maps. I will review current theories on the formation of such objects and present the results of recent three-dimensional radiative hydrodynamical models studying the fluid flow and energy transfer in the atmosphere of these close-in planets. In addition to helping understand observational results, the calculated efficiency of energy redistribution throughout the upper atmosphere, particularly to the night-side of the planet, may have consequences for evaporative processes, thermal tidal interactions, and the overall contraction of the planet.