Dynamical Evolution of Dense Stellar Systems Proceedings IAU Symposium No. 246, 2007 E. Vesperini, M. Giersz & A. Sills, eds. c  2008 International Astronomical Union doi:10.1017/S1743921308015408 Tidal Tails of the Nearest Open Clusters Yaroslav Chumak 1 and Alexey Rastorguev 2 1 Sternberg Astronomical Institute, Universitetskiy prospect 13, Moscow,119992, Russia email:chyo@mail.ru 2 Department of Physics, Moscow State University, GSP-2, Leninskiye Gory, Moscow, 119992, Russia email:rastor@sai.msu.ru Abstract. We show that an extended population of stars escaping an evolved cluster and moving along its galactic orbit forms at the final phases of its dynamical evolution. Here we present some results of the numerical simulations for nearest open clusters: Hyades, Pleiades, Praesepe, Alpha Persei, Coma, IC 2391, and IC 2602. We calculated the models of the stellar tails for nearest open clusters and estimated some parameters: sizes, densities, locations relative to the solar neighborhood. Stars of the nearest tails can be observed as moving clusters. Keywords. open clusters and associations: general, methods: n-body simulations In our simulations (Chumak, Rastorguev, & Aarseth 2005), (Chumak & Rastorguev 2006a) it was shown that stars escaped from a cluster at different times, move very close to cluster’s orbit. Their relative velocities are small but relative distances along the cluster orbit change from parsecs, to more than 1.5 kpc. As a consequence, escaped stars form a stretched stellar tail, which can exist for a fairly long time even after full disintegration of the open cluster as its relic. We performed simulations of the dynamical evolution of seven nearest clusters in the tidal field of the Galaxy (Chumak & Rastorguev 2006b). Our computations of the dynamical evolution have been based on the Aarseth’s code NBODY6 (Aarseth 2003), with known cluster age estimates and real Galactic orbits. Initial conditions have been chosen in such a way that current parameters of simulated clusters corresponded to their observed parameters (Nordstrom et al. 2004). Fig. 1 (left panel) shows the position of stellar tail relative to the cluster and its orbit for typical cluster with an age 1233 Myr. The right panel shows the close neighborhood of the cluster, ±200 pc. The results can be briefly summarized as follows: 1. The length of the cluster tails along the Galactic orbit, its thickness (along the Z axis), and its width (along the X axis) for a typical cluster (with N = 1500, initial virial radius RV =3.5 pc, an age of 800 Myr) can reach LY = 900 pc, LZ = 20 pc, and LX = 100 pc, respectively. 2. The stars in the tail may be considered as moving clusters, since their mean velocity vector is close to the velocity vector of the parent cluster and their internal velocity dispersion is relatively low(∼1 km s −1 ). 3. Hyades. The Hyades cluster lies inside the circumsolar sphere with the radius of 100 pc, and the cluster tail crosses this sphere and extends far beyond in both directions (see Fig. 2). The approximate length of the tail along the Y axis that falls within the circumsolar sphere is ∼160 pc. This sphere contains approximately 150 tail stars. 4. Coma. The tail of Coma cluster also crosses the circumsolar sphere. The approximate length of the tail along the Y axis that falls within the circumsolar sphere is ∼80 pc. The sphere contains about 80 tail stars. 107