DISCUSSIONS OF THE INTERNAL MOTIONS AND MASS SEGREGATION OF M67 ON THE BASIS OF ACCURATE PROPER MOTIONS

The radius and virial mass of the old open cluster M67 are presented. The internal motion and mass segregation of the cluster are also discu ssed on the basis of accurate stellar proper motions obtained combinin g three independent proper motion catalogues of the cluster. Increases of the mean proper motion and the intrinsic dispersion of member star s with radial distance from the cluster center might suggest that the stars are escaping from the cluster. The stars in both inner and outer regions appear to be in isotropic orbits. At last, it is found that b oth space and velocity mass segregations exist for the old open cluste r due to the dynamical evolution.