Planetary Systems in Star Clusters

About a third of stars in open star clusters of the Galaxy may have planetary systems. The increased density of stars in clusters introduces its own peculiarities into the evolution of their planetary systems. An analysis of the evolution conditions of planetary systems in star clusters has shown that close passages of cluster stars during its lifetime of ~3 × 108 years destroy the peripheral structures of planetary systems: asteroid–comet–planetary (ACP) spears, Kuiper belts. At the same time, the parts of planetary systems close to the star are not affected. As a result of the ACP, objects with major semi-axes of orbits exceeding ~17 AU are lost by planetary systems, forming the ACP of the cluster spear. The result of the cluster evolution after its disintegration is the formation of the ACP flow, coinciding with the stellar flow. The observed displacement of massive clusters of the Galaxy relative to the center of their stellar copies is a consequence of the gravitational braking of the clusters. It can be used to estimate the rotation parameters of the dark halo of the Galaxy with allowance for the asymmetry of the stellar copies of massive clusters caused by the gravitational braking of the nuclei.