Self-organization in gravitating many-body system

In the universe there exists various heavenly bodies corresponding to a wide range scale and they form hierarchical structure in it. It is one of the astrophysical big problems to elucidate a formation process or the dynamical structure of these heavenly bodies. In order to elucidate this problem, it is important to elucidate physical characters such as relaxation process in the gravitating many-body system where the gravity, which is a long-range force, controls motion, (quasi-) equilibrium state and steady-state stability, i.e., to elucidate self-organization in gravitating many-body system. In this chapter featuring difference between relaxation process in the system such as normal gas, where a short-range force controls motion, and that in the gravitating many-body system, self-organization with gravitating many-body system was explained. Chaotic itinerancies closely associated with relaxation process of self-gravitating systems, and thermal equilibrium were explained with need of new statistical mechanics for system with a long-range force. Finally reconstruction methods of the dynamical structure of the Galaxy by using observational data given by astrometry measurements (Japan Astrometry Satellite Mission for INfrared Exploration: JASMINE) were mentioned. (T. Tanaka)