The NASA Chandra Observatory Finds Black Holes Create Havoc
Black holes are creating havoc in unsuspected places, according to a
new study of images of elliptical galaxies made by NASA's Chandra
X-ray Observatory. The discovery of far-reaching explosive activity,
due to giant central black holes in these old galaxies, was a
surprise to astronomers.
The Chandra data revealed an unsuspected turmoil in elliptical
galaxies that belies their calm appearance in optical light.
Astronomers believe massive clouds of hot gas in these galaxies have
been stirred up by intermittent explosive activity from centrally
located super-massive black holes.
"This is another example of how valuable it is to observe the universe
at different wavelengths besides just the traditional optical
wavelengths," said NASA's Chandra Program Scientist Wilt Sanders.
"Without these X-ray and radio observations, we wouldn't know these
apparently static galaxies in reality are still evolving due to the
interaction with their central black holes."
These results came from an analysis of 56 elliptical galaxies in the
Chandra data archive by associate professor Thomas Statler and
doctoral candidate Steven Diehl, both of the Physics and Astronomy
department at the Ohio University, Athens, Ohio. Contrary to
expectations, they found the distribution of the multimillion-degree
gas in these galaxies differed markedly from that of the stars.
"Most elliptical galaxies have traditionally been considered to be
quiet places, like placid lakes," Statler said. "Our results show
these galaxies are a lot stormier than we thought."
Previous X-ray studies have shown elliptical galaxies contain
multimillion degree gas whose mass is a few percent of the stars in
it. Except for rare cases, violent activity in elliptical galaxies
was thought to have stopped long ago. It was expected the hot gas
would have settled into an equilibrium shape similar to, but rounder,
than the stars. High angular resolution imaging observations by
Chandra indicate otherwise.
"We found the distribution of hot gas has no correlation with the
optical shape," Diehl said. "Something is definitely making a mess
there, and pumping energy equivalent to a supernova every century
into the gas."
Although supernovae are a possible energy source, a more probable
cause was identified. The scientists detected a correlation between
the shape of the hot gas clouds and the power produced at radio
wavelengths by high-energy electrons. This power output can be traced
back to the centers of the galaxies, where super-massive black holes
Repetitive explosive activity fueled by the in-fall of gas into
central black holes is known to occur in giant elliptical galaxies
located in galaxy clusters. Statler and Diehl's analysis indicates
the same phenomena are also occurring in isolated elliptical
"These results are part of an emerging picture that shows the impact
of super-massive black holes on their environment is far more
pervasive than previously thought," Statler said.