Astronomers from UC Berkeley have identified 33 pairs of
waltzing black holes, closing the gap somewhat between the
observed population of super-massive black hole pairs and what
had been predicted by theory. "Astronomical observations have
shown that 1) nearly every galaxy has a central super-massive
black hole (with a mass of a million to a billion times the mass
of the Sun), and 2) galaxies commonly collide and merge to form
new, more massive galaxies. As a consequence of these two
observations, a merger between two galaxies should bring two
super-massive black holes to the new, more massive galaxy formed
from the merger. The two black holes gradually in-spiral toward
the center of this galaxy, engaging in a gravitational tug-of-
war with the surrounding stars. The result is a black hole
dance, choreographed by Newton himself. Such a dance is expected
to occur in our own Milky Way Galaxy in about 3 billion years,
when it collides with the Andromeda Galaxy." coondoggie writes
"NASA is looking to reduce the d