Q&A: Black Holes

Q:
Is it possible that a system of two black holes could exist in orbit, such that at a point during their orbits their event horizons cross, causing an area of space to be within both event horizons? If so, what would happen to objects in this area?

A:
If two black holes come close enough to each other that their event horizons cross, they have effectively merged. The area of the event horizons is combined into one large event horizon, and objects which cross this large event horizon fall in, never to be seen again, the same as if an object had passed into one of the original event horizons.

Chandra has observed what we believe is the merging process of 2 massive black holes in a beautiful butterfly shaped galaxy called NGC 6240. For images and details on the future of this galaxy, please see this page:
http://chandra.harvard.edu/photo/2002/0192/index.html

To view all the black holes observed by Chandra thus far, visit:
http://chandra.harvard.edu/photo/category/blackholes.html

For more information on black holes, including how the mass is determined:
http://chandra.harvard.edu/learn_bh.html