Examining the M67 Classification as an Open Cluster

• 作者: Evgeny Griv Shimmon Naim
• 来源期刊: 天文学与天体物理学国际期刊(英文)
• 学科: 医学
• 关键词: PHOTOMETERS Techniques PHOTOMETRIC Open CLUSTERS and Associations M67 GALAXIES STAR CLUSTERS
• 年，卷（期）: 2012,（3）
• 页码范围: 167-173
• 页数: 7页
• 分类号: R73

摘要

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 “open cluster” shape due to the dynamical evapora-tion of the majority of its stars.