Internal kinematics of open star clusters

Abstract

Proper motion data have been used to study the internal kinematics in eight open star clusters. The dependence of the intrinsic dispersion in proper motion on stellar mass and radial distance from the cluster centre have been studied. In most clusters no such dependence is observed. Velocity isotropy has been observed in all the clusters studied here, except in NGC 2516, in which the radial and tangential components of the intrinsic velocity dispersion are different in the outer regions (R > 2 pc) of the cluster.