The orbital evolution of planets orbiting ageing stars

Some 95% of all stars in the galaxy have an initial mass lower than 8 solar masses; it is now thought that the majority has at least one planetary companion. During the post-main-sequence evolution, these stars go through giant phases characterized by significant mass loss, large stellar radii, strong pulsations, and extreme luminosities. These changes in stellar characteristics may completely transform a planetary system: the stellar wind, star-planet tides, planet accretion or loss rates, and drag forces drive the orbital evolution of the giant star-planet system and establish whether the planet survives the star’s giant phases or not. But, at present time, the orbital evolution of planets orbiting giant stars is only addressed at the level of the stellar equilibrium tide, with mass-loss rate prescriptions and mass-transfer efficiencies now thought to be inaccurate. Here I take a radically different approach by constructing models that include all relevant ingredients and are based on unprecedented calculations. I will extend the tidal formalism with pioneering calculations of dynamical tides in giant stars and will include spin-orbit coupling, wind Roche Lobe overflow, gravitational and frictional drag forces, novel planet accretion and loss rates and a new wind mass-loss rate relation. That way, this project will lead to a new quantitative metric for predicting the fate of planets orbiting ageing stars, including that of the Solar system planets orbiting the ageing Sun.