One of the most popular N-body models that has been under investigation in the last ten years, is the so-called ring problem of (N+1) bodies, otherwise known as the regular polygon problem of (N+1) bodies. Here we present an overview of the scientific work that has been done throughout these years as well as the major results obtained so far. An extended bibliography is displayed at the end of this article, aiming to become a source of information for further analytical study.
1. INTRODUCTIONThe ring problem of (N+1) bodies describes the motion of a small body S which moves in the force field created by N major bodies called the primaries. The ν=N-1 of them, have equal masses and are located at the vertices of an imaginary ν-gon. The N-th body has a different mass and is located at the center of mass of this formation (Figure 1). Figure 1. The general configuration of the ring problem of (N+1) bodiesThe problem is characterized by two parameters: the number ν of the peripheral primaries and the mass parameter β which is the ratio of the central mass m 0 to a peripheral one named m. The regular polygon formation of the big bodies with another one at their center of mass was proposed by Maxwell in 1865 [1] in order to explain the rings of Saturn. Since then, this configuration has often been found to be the center of special scientific interest and many papers have been written aiming to prove its central character and to find homographic solutions, relative equilibria, conditions for stability etc. not only for the simple gravitational case but also for cases that include post-Newtonian potentials ([2]-[21]). However, the ring problem as a new dynamical system under the description made at the beginning of this paragraph, first appeared in Scheeres' PhD Thesis ([22]) and a little later in a joint paper with Vinh ([23]). The problem was considered anew by the author of the present articles and his collaborators, who devoted ten years (1999)(2000)(2001)(2002)(2003)(2004)(2005)(2006)(2007)(2008)(2009) of scientific research in investigating many of its aspects ([24] -[48]). He reformulated the whole problem and he improved the original model by considering not only gravitational forces but also forces coming either from radiation or from post-Newtonian potentials. He also examined some cases where the small body is a tri-axial body or a gyrostat. The configuration is quite simple and, apart from other benefits, can be reduced to some already known problems-models of