The Absolute Proper Motion Of M3 And Its Orbit In The Galaxy

14 plates of globular cluster M3, taken with the 40cm refractor atSheshan station of Shanghai Astronomical Observatory, are used by thiswork. The difference of epoch of these plates is up to 81years. Thepositions and absolute proper motions of 24 stars in ACT catalogue,which links with the Hipparcos Catalogue based on the InternationalCelestial Reference System, are used as the reference frame. Using thecentral overlapping principle, the absolute proper motions of 534 stars inthe region of about 100'×100' around the cluster are determined. After themembership determination of the stars which based on the data of propermotions, average absolute proper motion components for the cluster of-0.3±0.3 mas/yr in R.A. and -3.1±0.3 mas/yr in Dec. are obtained.Combining our results with the known distance and radial velocity of thecluster, we calculate its orbits in Galaxy using two given three-componentGalactic potential models and analyse its spatial motion in our Galaxy.We discuss the effect on the cluster's orbits caused by different Galacticpotential models and different values of the cluster proper motion.