A Kerr black hole has a theoretical rotation component due to conservation of angular momentum. It cannot be measured directly as we cannot observe anything occuring inside the event horizon. I doubt it's meaningful to talk about rotataion with respect to the event horizon. For discussion, see http://science.howstuffworks.com/black-hole.htm/printable
I heard in class of a theorie that would use the light emmited from the black hole surroundings to calculate the rotation speed, anyone familiar with these theories?
thanks
I heard about that. In an x-ray binary in which a black hole is believed to be the compact object, it has been suggested that the strength of an ultrasoft x-ray component is directly related to the black hole's spin.
Check out section 8.2 of the following: http://arjournals.annualreviews.org/doi/abs/10.1146/annurev.astro.44.051905.092532