Kerr ring singularity
= Kerr ring singularity
{c}
{title2=$r=0,\quad\theta=\pi/2$}
For nonzero spin, the curvature singularity of the <Kerr metric> is the ring $x^2+y^2=a^2$, $z=0$ in oblate Cartesian coordinates. The rest of the $r=0$ disk is regular and allows continuation to negative $r$. The entire disk must not be mistaken for a curvature singularity, and axial trajectories do not hit the ring.