Kerr ergoregion
= Kerr ergoregion
{c}
= Ergoregion
{synonym}
The Kerr ergoregion is the region where the asymptotically timelike stationary Killing field becomes spacelike. Its outer boundary is $r=M+\sqrt{M^2-a^2\cos^2\theta}$.
The Kerr realization of an <ergosphere> lies outside the outer horizon where the stationary Killing vector is spacelike; its outer boundary is $r=M+\sqrt{M^2-a^2\cos^2\theta}$.