An Etymological Dictionary of Astronomy and Astrophysics
English-French-Persian

The process whereby a system of gravitationally interacting particles attains stability. The comparable mass components interact with each other, but the whole system does not expand or collapse. Virialization occurs when the → potential energy is twice the negative → kinetic energy: - W_vir = 2 K_vir (→ virial theorem). In the case of a → galaxy cluster, when the cluster is virialized the merging process and the collapse of matter have finished and the formation process of the galaxy cluster is considered to be done. A cluster has formed by → hierarchical clustering. Virialized clusters, in other words finished clusters, can be found by looking at their radius and density. A cluster is virialized when it satisfies the condition: R_vir ~ R_max/2, where R_vir is the radius when the cluster is virialized and R_max is the radius when the collapse starts. From this condition it follows that the object is 8 times denser at virialization than when the collapse started.

Verbal noun of → virialize.