The Kerr solution and black hole spin

Assembled from 13 blocks · 2 evidence · 13 related

1. Story
2. Roy Kerr found the exact vacuum solution for a rotating mass in 1963, forty-seven years after the static case, and it is the one that describes real black holes: everything that collapses carries angular momentum. Spin is bounded, conventionally written as a dimensionless parameter that cannot exceed one, and it changes the geometry substantially. The horizon contracts as spin rises. Outside it lies the ergosphere, a region in which spacetime is dragged around so strongly that no observer can remain stationary relative to distant stars, and from which Penrose showed in 1969 that rotational energy can in principle be extracted. The innermost stable circular orbit moves inward with prograde spin, which raises the efficiency with which infalling matter can radiate. Astrophysical black holes are described by mass and spin alone; electric charge is neutralised by the surrounding plasma on very short timescales. Not a place on Earth.
3. Knowledge
4. The Kerr solution and black hole spin
5. Connections
6. The event horizon
7. The no-hair result
8. Innermost stable circular orbit
9. Kerr finds the rotating solution
10. A mechanism for extracting energy from a spinning black hole
11. Evidence
12. The exact vacuum solution for a rotating mass, which is the geometry that applies to astrophysical black holes. V55 VERIFICATION BASIS: not consulted in session; no research tool was available. Title, volume and page are from recall and must be checked.
13. Revises the distance to Cygnus X-1 by radio parallax and with it the mass of the compact object, to approximately 21 solar masses. V55 VERIFICATION BASIS: not consulted in session; no research tool was available. Title wording, volume and page are from recall and must be checked; the near-maximal spin inference reported alongside is model-dependent.