Kerr black hole
= Kerr black hole
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= Kerr spacetime
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{synonym}
The Kerr black hole is the asymptotically flat stationary axisymmetric vacuum black hole with mass $M$ and angular momentum $J=Ma$.
A Kerr black hole is the <Kerr metric> with mass $M>0$ and spin parameter satisfying $|a|\leq M$ in geometrized units; its outer horizon is $r_+=M+\sqrt{M^2-a^2}$.