Deciphering Star Cluster Evolution by Shape Morphology

We analyze the morphological evolution of open clusters and provide shape parameters for 265 clusters. The results show that overall sample becomes more elliptical as they grow older, while their core remains circular or slightly trend to circularize. There is a negative correlation ellipticities with number members A significant between masses also detected log(age/year) $\geq$ 8, suggesting shapes are possibly influenced by masses, in addition external forces surrounding environment. For most young clusters, radial stratification degree short axis direction greater than long, implying two directions within cluster may be unevenly affected an internal evolutionary process. Older exhibit lower tangential direction, which means those continue survive long time at low level stratification. Our analysis shows susceptible influence Galactic tides toward center shear embedded differential rotation. By analyzing distribution ages star we suggest NGC 6791 originate from superclusters.