Tidal flows in extrasolar planets

Part of the applied mathematics seminar series.

The discovery and partial characterisation of several thousand planets orbiting stars other than the Sun is the most exciting development in modern astrophysics. Many of these planets orbit their stars much more closely than Mercury orbits the Sun, and some have been found to orbit in less than one Earth day. At such distances, tidal gravitational interactions between these planets and their host stars can have important effects on the planetary orbit and the stellar and planetary spins. In particular, it is thought that the dissipation of tidally-excited flows inside short-period planets can explain why their orbits tend to be circular, in comparison to those that orbit more distantly, which have a wide range of orbital eccentricities. However, the mechanisms of tidal dissipation are not well understood theoretically. I will first introduce the subject area, before presenting some previous and ongoing work which aims to understand the mechanisms of tidal dissipation in the fluid layers of planets (and stars) from first principles, and ultimately to explain the astrophysical observations.