The frequency distribution f ( a ) of major semiaxes of double and multiple systems , and their eccentricities and mass ratios , contain valuable fossil information about the process of star formation and the dynamical history of the systems .
In order to advance in the understanding of these questions , we made an extensive analysis of the frequency distribution f ( a ) for wide binaries ( a > 25 AU ) in various published catalogues , as well as in our own ( Poveda \etal 1994 ; Allen \etal 2000 ; Poveda & Hernández-Alcántara 2003 ) .
Based upon all these studies we have established that the frequency distribution f ( a ) is function of the age of the system and follows Oepik ’ s distribution f ( a ) \sim 1/ a in the range of 100 AU < a < a _ { c } ( t ) , where a _ { c } ( t ) critical major semiaxis beyond which binaries have been dissociated by encounters with massive objects .
We argue that the physics behind the distribution f ( a ) \sim 1/ a is a process of energy relaxation , analogous to those present in stellar clusters ( secular relaxation ) or in the early stages of spherical galaxies ( violent relaxation ) .
The existence of runaway stars indicates that both types of relaxation are important in the process of binary and multiple star dynamical evolution .