MadSci Network: Astronomy |
Well, actually, black holes are thought to have only three properties: mass, electrical charge, and angular momentum. So the rotation (or more specifically, the angular momentum) of the material that falls into the black hole is indeed preserved. Since it would be very unusual for the material falling into a black hole not to have any angular momentum, it is expected that all black holes will indeed rotate. A rotating black hole is called a Kerr black hole.
How does the angular momentum show up? Well, the rotating black hole actually drags space-time along with it as it rotates. Here are some Web pages that describe what goes on:
Jillian's Guide to Black Holes: Jillian's Guide to Black Holes
Animation of the accretion disk around a rotating black hole (this is an Mpeg): Black Hole Animation
Kerr's Rotating Black Holes (a full mathematical description, not for the faint of heart!): http://www.astro.ku.dk/~cramer/RelViz/text/geom_web/node4.html
Hope this helps!
Try the links in the MadSci Library for more information on Astronomy.