# 5: Spinning Black Holes


• 5.1: The Kerr Metric
The Schwarzschild metric assumes that the object at the center is completely stationary. Almost all spherical objects in space, however, spin. This is even true for black holes, which form when a star collapses. Since the progenitor star spins, by conservation of angular momentum the resulting black hole must spin as well. This spinning destroys the azimuthal symmetry, which in turn means that we need a different metric to describe spinning, spherical objects.
• 5.2: Constants of Motion
When studying the Schwarzschild metric, we used the geodesic equation to determine constants of motion, which in turn gave us hints about how particles move.
• 5.3: The Ergoregion
For a Schwarzschild black hole, the infinite redshift surface, the static limit surface, and the event horizon happen to have the same r-value, but that isn't necessarily the case for other black holes. For a spinning black hole, the infinite redshift surface and the static limit surface are still the same, but they are different from the event horizon. The region in between the infinite redshift surface and the event horizon is called the ergoregion.

Thumbnail: This artist's concept illustrates a supermassive black hole with millions to billions times the mass of our sun. Supermassive black holes are enormously dense objects buried at the hearts of galaxies. (Public Domain; NASA/JPL-Caltech).

This page titled 5: Spinning Black Holes is shared under a not declared license and was authored, remixed, and/or curated by Evan Halstead.