%0 Journal Article %T Examining the M67 Classification as an Open Cluster %A Shimmon Naim %A Evgeny Griv %J International Journal of Astronomy and Astrophysics %P 167-173 %@ 2161-4725 %D 2012 %I Scientific Research Publishing %R 10.4236/ijaa.2012.23020 %X The cluster M67 (= NGC 2682) in Cancer is a rich stellar cluster, usually classified as an open cluster. Using our own observations with the 0.4 m telescope, we show that M67 is a tight group of about 1200 stars. The actual radius of the cluster is about 3.1 pc and the average mass of a star in the system is about . We also show that the ratio of the mean kinetic energy of the cluster to its mean gravitational potential energy , while the value predicted by the virial theorem is equal to . So the system is a gravitationally bound. This value of is considered as an evidence of quasi-stability of the cluster and allows us to use the Chandrasekhar-Spitzer relaxation time for M67 Myr as a characteristic dynamical relaxation time of the system. As the cluster is almost twice older its half-life time , it is argued that M67 was in the past (about 4 Gyr ago, close to its forma-tion) a relatively small ( stars) globular cluster, but got ˇ°open clusterˇ± shape due to the dynamical evapora-tion of the majority of its stars. %K Photometers %K Techniques %K Photometric %K Open Clusters and Associations %K M67 %K Galaxies %K Star Clusters %U http://www.scirp.org/journal/PaperInformation.aspx?PaperID=23253