Innermost stable circular orbit

Assembled from 17 blocks · 2 evidence · 20 related

1. Story
2. The last orbit matter can hold before it must fall. Newtonian gravity permits a stable circular orbit at any radius; general relativity does not, and below a critical radius every circular orbit is unstable, so an inspiralling particle spirals in over a few orbits rather than drifting slowly. For a non-rotating black hole the radius is six GM over c-squared - three Schwarzschild radii - and it moves inward for prograde orbits around a spinning hole, approaching the horizon in the extremal limit. This single number sets the efficiency of accretion, because it fixes how much gravitational binding energy can be radiated before the material is lost. About 5.7 per cent of the rest mass for a non-rotating hole, and up to something over 40 per cent for a maximally spinning one. Hydrogen fusion converts about 0.7 per cent. That comparison is why accretion onto black holes is the most efficient sustained energy release known in astrophysics. Not a place on Earth.
3. Knowledge
4. The Kerr solution and black hole spin
5. Innermost stable circular orbit
6. Connections
7. The Kerr solution and black hole spin
8. Accretion disc
9. Kerr finds the rotating solution
10. The event horizon
11. The no-hair result
12. Innermost stable circular orbit
13. Kerr finds the rotating solution
14. A mechanism for extracting energy from a spinning black hole
15. Evidence
16. The standard thin accretion disc model, parameterising angular-momentum transport by a single viscosity coefficient. V55 VERIFICATION BASIS: not consulted in session; no research tool was available. Title, volume and page are from recall and must be checked.
17. 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.