Planetary Astrophysics

Different physical mechanisms are involved in the process of planet formation, starting from the evolution of the dust and gas in a circumstellar disk to the growth of pebbles and planetesimals, which finally accumulate into planets. These mechanisms lead to a very diverse population of planets present in our solar system and in the vast number of extrasolar planetary systems recently discovered. Additional physical processes influence the interaction of planets with their environment and the central star. The presence of a magnetic field is, for example, an essential ingredient for the habitability of a planet, which will be protected by the stellar wind. In this book I try to give a comprehensive outline of all these physical mechanisms involved in sculpting a planetary system and its environment. The most relevant are gravitational and tidal interactions, absorption and re-emission of the star light, magnetic fields and their interaction with the solar wind and the dynamics of fluids, which govern the evolution of circumstellar disks. An effort has been devoted to outline their mathematical aspects and their implications in determining the observed physical and dynamical properties of the known planetary systems. Only essential references are given, quoting the authors of a scientific paper whenever a figure is taken from it. Most topics are part of the lecture notes from the course “Planetary Astrophysics” at the University of Padova in Italy, and it is intended for graduate and post-graduate students and researchers who are new to the field.