World Library  
Flag as Inappropriate
Email this Article

Rotating black hole

Article Id: WHEBN0000701158
Reproduction Date:

Title: Rotating black hole  
Author: World Heritage Encyclopedia
Language: English
Subject: Black hole, Schwarzschild radius, Penrose process, Naked singularity, Photon sphere
Collection: Black Holes
Publisher: World Heritage Encyclopedia
Publication
Date:
 

Rotating black hole

A rotating black hole is a black hole that possesses angular momentum. In particular, it rotates about one of its axes of symmetry. This seems paradoxical in regards of the time slow down near the black hole.

The two physical relevant surfaces of a Kerr black hole.

Contents

  • Types of black holes 1
  • Formation 2
    • Relation with gamma ray bursts 2.1
  • Conversion to a Schwarzschild black hole 3
  • Kerr metric, Kerr–Newman metric 4
  • See also 5
  • References 6
  • Further reading 7

Types of black holes

There are four known, exact, black hole solutions to Einstein's equations, which describe gravity in General Relativity. Two of these (the Kerr and Kerr–Newman black holes) rotate. It is generally believed that every black hole decays rapidly to a stable black hole; and, by the no-hair theorem, that (except for quantum fluctuations) stable black holes can be completely described at any moment in time by these eleven numbers:

These numbers represent the conserved attributes of an object which can be determined from a distance by examining its electromagnetic and gravitational fields. All other variations in the black hole will either escape to infinity or be swallowed up by the black hole. This is because anything happening inside the black hole horizon cannot affect events outside of it.

In terms of these properties, the four types of black holes can be defined as follows:

Non-rotating (J = 0) Rotating (J > 0)
Uncharged (Q = 0) Schwarzschild Kerr
Charged (Q ≠ 0) Reissner–Nordström Kerr–Newman

Formation

Rotating black holes are formed in the gravitational collapse of a massive spinning star or from the collapse of a collection of stars or gas with a total non-zero angular momentum. As most stars rotate it is expected that most black holes in nature are rotating black holes. In late 2006, astronomers reported estimates of the spin rates of black holes in the Astrophysical Journal. A black hole in the Milky Way, GRS 1915+105, may rotate 1,150 times per second,[1] approaching the theoretical upper limit.

Relation with gamma ray bursts

The formation of a rotating black hole by a collapsar is thought to be observed as the emission of gamma ray bursts.

Conversion to a Schwarzschild black hole

A rotating black hole can produce large amounts of energy at the expense of its rotational energy. This happens through the Penrose process in the black hole's ergosphere, an area just outside its event horizon. In that case a rotating black hole gradually reduces to a Schwarzschild black hole, the minimum configuration from which no further energy can be extracted, although the Kerr black hole's rotation velocity will never quite reach zero.

Kerr metric, Kerr–Newman metric

A rotating black hole is a solution of Einstein's field equation. There are two known exact solutions, the Kerr metric and the Kerr–Newman metric, which are believed to be representative of all rotating black hole solutions, in the exterior region.

See also

References

  1. ^ Black hole spins at the limit | COSMOS magazine

Further reading

  • C. W. Misner, K. S. Thorne, J. A. Wheeler, J. Wheeler, and K. Thorne, Gravitation (Physics Series), 2nd ed. W. H. Freeman, September 1973.
  • Melia, Fulvio, The Galactic Supermassive Black Hole, Princeton U Press, 2007
  • Macvey, John W., Time Travel, Scarborough House, 1990
This article was sourced from Creative Commons Attribution-ShareAlike License; additional terms may apply. World Heritage Encyclopedia content is assembled from numerous content providers, Open Access Publishing, and in compliance with The Fair Access to Science and Technology Research Act (FASTR), Wikimedia Foundation, Inc., Public Library of Science, The Encyclopedia of Life, Open Book Publishers (OBP), PubMed, U.S. National Library of Medicine, National Center for Biotechnology Information, U.S. National Library of Medicine, National Institutes of Health (NIH), U.S. Department of Health & Human Services, and USA.gov, which sources content from all federal, state, local, tribal, and territorial government publication portals (.gov, .mil, .edu). Funding for USA.gov and content contributors is made possible from the U.S. Congress, E-Government Act of 2002.
 
Crowd sourced content that is contributed to World Heritage Encyclopedia is peer reviewed and edited by our editorial staff to ensure quality scholarly research articles.
 
By using this site, you agree to the Terms of Use and Privacy Policy. World Heritage Encyclopedia™ is a registered trademark of the World Public Library Association, a non-profit organization.
 


Copyright © World Library Foundation. All rights reserved. eBooks from Project Gutenberg are sponsored by the World Library Foundation,
a 501c(4) Member's Support Non-Profit Organization, and is NOT affiliated with any governmental agency or department.