Tides and Atmospheres for Hot Jupiters

Princeton University, Princeton NJ

Investigators

Abstract

AST 0707373 Goodman At this time, there are at least forty extrasolar planets orbiting main-sequence stars with well-determined periods of less than 10 days and minimum masses less than 10 Jupiter masses. The discovery of these "hot Jupiters" defied previous experience based on the Solar System. Their detailed orbital and physical properties present several specific mysteries, which are probably clues to their origins, internal structure, and early protostellar environment. Why are their masses significantly smaller on average than those of planets with longer periods? Why do the periods peak at ~3 days? Why are their orbits less eccentric? Presuming that they formed on larger orbits and migrated inward, why did the hot Jupiters not migrate all the way into their stars, or do we see only the lucky survivors of a much larger initial population? Were "hot Neptunes" once hot Jupiters that suffered severe mass loss? Among the few hot Jupiters that have well-determined radii by virtue of transiting their stars, why are many of these radii significantly larger or smaller than straightforward models predict? It is likely that many of the solutions involve tidal or radiative interactions between the planet and its star, as these influences depend strongly on orbital distance. Building upon past experience with tides and other problems in astrophysical fluid dynamics, Dr. Jeremy Goodman's research team will investigate the interrelations between tidal dissipation, irradiation, and mass loss, with particular attention to the outer layers of hot Jupiters. The tools will be semianalytic estimates and one dimensional calculations rather than multidimensional simulations. Tidal dissipation is among the oldest unsolved problems in theoretical astronomy. Because of their low surface gravity and inability to burn hydrogen, hot Jupiters are structurally more sensitive to tidal dissipation than stars and may better preserve a "memory" of past tidal influences. So the study of these objects may yield insights applicable to tidal interactions more generally. Besides, extrasolar planets are of great interest to the public as well as to professional astronomers because of the lessons they may have to teach about the history of our own solar system, and perhaps even the possibilities for life beyond earth. ***