Astrophysics of high energy

Violent phenomena in the Universe are connected to the presence of very compact objects, neutron stars or black holes. It is only very recently that black holes have acquired the status of astrophysical objects, and not just curiosities of the theory of gravitation (singularities protected by a horizon, whereas the big bang is a naked singularity). Indeed, black holes seem to be ubiquitous in the Universe: they represent the final stage of a star, are present in many binary systems, but also at the centre of most galaxies (such as our own). And, even though they are rather simple objects from the point of view of gravity, their environment is very complex. Indeed, the understanding of how high-energy phenomena recycle energy into their environment and the feedback to large distances of powerful explosions, jets, and the impact of their companion high-energy particles are keys to understanding the emergence of new structures (clouds, stars, galaxies) in the Universe. All require high precision observations and elaborated modeling.