5 - Astroparticle Physics, Gravitational Waves, and Space Physics

Summary

After a general description of the concepts and studies addressed by astroparticle physics, as a major discovery representative of the beauty of this research area, the chapter presents the origin and the solution of the solar neutrino problem. Then, it introduces the new astronomical window of gravitational wave astronomy, commenting on the extraordinary event, GW 170817, for which the so-called electromagnetic counterparts have been observed. Space physics is then addressed because of its distinctive feature of being at the interface between physics and astrophysics (also in relation to the problem of dark matter). In fact, in situ measurements in various regions of the solar system have allowed us to collect data that are very similar to those obtained in laboratory experiments. A central focus of interest is the structure and dynamics of space plasmas, in particular of the solar wind and its interactions with the interstellar medium. The dynamical digression closing the chapter describes a well-known effect in celestial mechanics that has played a key role in interplanetary navigation, that is, the so-called slingshot. The digression offers an excuse for mentioning a hot topic on the grand scale of galaxies, in which gravity assists can produce hypervelocity stars, an interesting phenomenon currently under investigation.