Stellar crossing time
= Stellar crossing time
{title2=$t_{\rm dyn}\sim R/v$}
The <stellar crossing time> is a characteristic <time> to traverse a system, $t_{\rm dyn}\sim R/v$. In a virialized self-gravitating system, $v^2\sim GM/R$, so $t_{\rm dyn}\sim\sqrt{R^3/(GM)}$. It is distinct from the much longer spherical <stellar relaxation time>. Radius versus diameter and characteristic-speed conventions change order-one factors.