How Stellar Tides Affect Planet Evolution

Sammanfattning: Planets that orbit their host star closely experience tidal forces due to the strength of gravity not being uniform all over the planet. This leads to effects such as tidal spin synchronization, tidal eccentricity damping and tidal semi-major axis damping. This project aims to study how the time scales for these phenomena are affected by the planetary parameters such as mass, radius and the tidal dissipation quality factor Q as well as the initial value of the semi-major axis. Simulations were made using an averaging code which was based on the fact that the Runge-Lenz vector e and the orbital angular momentum vector h vary slowly under external perturbations such as tidal forces. Because of this the average of these vectors can be used to calculate orbital elements instead of using N-body simulations which decreases the calculation time. We found that the time scales were of different orders of magnitude, with the spin time scale of the order of 10^4 years, the eccentricity time scale of the order of 10^7 years and the semi-major axis time scale of the order of 10^8 years. An increase of mass and the Q-value both increased the time scale while an increase of radius decreased the time scale. For the initial value of the semi-major axis a lower value gives a shorter time scale compared to larger values.