Centrifugal barrier
= Centrifugal barrier
{title2=$V_{\rm eff}(r)=\Phi(r)+L^2/(2r^2)$}
For a central <gravitational potential> and nonzero <specific angular momentum> $L$, the positive $L^2/(2r^2)$ contribution to the radial <effective potential> can prevent the orbit reaching the centre at finite energy. It dominates the attractive $-\mu/r$ term at small $r$ in a <Kepler orbit>. A more singular attractive term may overcome it: for $\Phi=-\mu/r-\mu a/r^2$, the net inverse-square coefficient is $(L^2-2\mu a)/2$, so a central barrier exists only when that coefficient is positive.