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Can we assume that most (if not all) black holes are rotating, due to conservation of momentum?

I am excluding the micro world from this question, just thinking of the range of stars on the main sequence of the H-R diagram as they shrink over time.

Can anyone give me an example of non-rotating macro sized B.H., e.g a binary system where each star counter-rotates relative to the other and explain how they may, (if they can) at least slow down each others's rotational velocity?

Qmechanic
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Yes, we expect all astrophysical black holes to have nonzero rotation. If nothing else, a rotating black hole that absorbs even a single particle with net angular momentum will then have nonzero angular momentum.

Zo the Relativist
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  • That's a very good reference that @Qmechanic gave me (and am I kicking myself ...yes). But then two quick implications: Solving the Schwardschild solution is purely a teaching aid rather than reality and to sum up can we (crudely, I know) ultimately derive macro spin from scaled up inherent particle spin? –  Apr 08 '15 at 18:44
  • @irishphysics: well, I wouldn't say that Schwarzschild is useless. It's TREMENDOUSLY less complicated than Kerr, and the kerr corrections fall off a factor of $r$ faster than the schwarzschild terms, so for many cases, schwarzschild is perfectly good. Not to mention all o fhte birchoff-style reuslts you can get. – Zo the Relativist Apr 08 '15 at 19:11
  • but yes, I wouldn't conclude too much from kruskal topology. – Zo the Relativist Apr 08 '15 at 19:12