Imagine the Universe!
Imagine Home  |   Ask an Astrophysicist  |  
Ask an Astrophysicist

The Question

(Submitted July 11, 2001)

What would happen if two Black Holes merged? Would superpositioning of the gravitational fields make the event horizon radii shrink?

The Answer

The size of the event horizon is determined solely by the mass and spin (if it happens to be spinning) of the black hole. If two were to orbit each other (or any two massive bodies such as neutron stars) a lot of energy in the form of gravity waves would be emitted. This will leak energy out of the system, until the two objects merge. It would appear that the smaller one was swallowed by the larger, but it really is a merger around their common center of mass, and the event horizon would grow according to the new higher mass.

Also there is more information on this at:

http://www.astronomical.org/oldsite/portal/modules/wfsection/article.php?articleid=141
http://archive.ncsa.uiuc.edu/Cyberia/NumRel/BlackHoleAnat.html
http://archive.ncsa.uiuc.edu/Cyberia/NumRel/GravWaves.html
http://lisa.jpl.nasa.gov/SCIENCE/mbh.html

Two experiments which hope to detect and confirm this can be seen at:

http://archive.ncsa.uiuc.edu/Cyberia/NumRel/LIGO.html
http://lisa.jpl.nasa.gov/

Hope this helps,
Michael Arida for Ask an Astrophysicist

Previous question
Prev
Main topic
Main
Next question
Next

If words seem to be missing from the articles, please read this.

Imagine the Universe! is a service of the High Energy Astrophysics Science Archive Research Center (HEASARC), Dr. Alan Smale (Director), within the Astrophysics Science Division (ASD) at NASA's Goddard Space Flight Center.

The Imagine Team
Project Leader: Dr. Barbara Mattson
Curator: J.D. Myers
Responsible NASA Official: Phil Newman
All material on this site has been created and updated between 1997-2014.
This page last updated: Thursday, 23-Oct-2008 11:18:04 EDT