Diagram of the static limit (ergosphere) and the inner and outer event horizons of a rotating black hole.<br>
"a" is the Spin parameter of the rotating black hole; with a low spin-parameter the ergosphere converges to an ellipsoid, while with a high spin-parameter it resembles a pumpkin-shape. The axes are in units of GM/c². If a=0 both coordinate systems reduce to Schwarzschild.
<a href="//commons.wikimedia.org/wiki/User:Yukterez" title="User:Yukterez">Yukterez (Simon Tyran, Vienna)</a>
CC BY-SA 4.0
<span class="int-own-work" lang="en">Own work</span>