"Hydrogen-Helium Mixtures in Interior of Giant Planets"

Burkhard Militzer, Carnegie Institute

Wednesday, November 2, 2005 4:00 pm Goldwater Building, Room 487 Light refreshments at 3:45 p.m. Host: John Shumway

ABSTRACT:

The properties of hydrogen-helium mixtures at high pressure are crucial to address important questions about the interior of giant planets e.g. whether Jupiter has a rocky core and whether it was formed by core accretion. Understanding dense, fluid hydrogen and helium is also of interest for the characterization of the more than 160 extrasolar giant planets that have be detected in recent years by radio velocity measurements. Using first principles simulations, we study the properties of hydrogen-helium mixtures as a function of pressure, temperature and composition. We derive an equation of state and make predictions for forth-coming shock wave experiments. Shock wave measurements are the only laboratory technique available today to directly probe the conditions present in the interior of giant planets. Our calculations demonstrate that the shock properties of helium differ substantially from those of hydrogen. We make suggestions for new shock experiments of helium in order to validate the hydrogen experiments and to understand processes giant planet interiors. Our calculations will also become relevant for the interpretation of the gravitational moments that will be measured by the Jupiter orbiter mission Juno to be launched under NASAs New Frontiers program.