Abstract

A short review of the multiple star studies is presented. Various methods of observations and orbit constructing for multiple stars are discussed --- visual, specle-interferometric, spectroscopic, photometric etc. The basic goal of such studies is to understand the origin and evolution of multiple stars. A new scheme of multiple star classification is suggested: a) Trapezia; b) high-hierarchical; c) intermediate class --- low-hierarchical systems. The systems of the first class are unstable (the seldom exceptions are motions in the vicinities of stable periodic orbits). High-hierarchical systems are probably stable (possible exceptions are the systems with very strongly elongated orbits of outer pairs). The low-hierarchical systems can be either stable or unstable. A list of low-hierarchical multiple systems is compiled. Their main parameters (orbital elements and masses of components) are determined. A reliability of their orbits and masses, actual system multiplicity and other properties are discussed. The results of stability analysis for a few such systems are given. Scenaria of unstable system formation are proposed.