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NASA's Chandra Finds Black Holes Are 'Green'



 
 
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Default NASA's Chandra Finds Black Holes Are 'Green'

April 24, 2006

Erica Hupp/Grey Hautaluoma
Headquarters, Washington
(202) 358-1237/0668

Steve Roy
Marshall Space Flight Center, Huntsville, Ala.
(256) 544-6535

Megan Watzke
Chandra X-ray Center, Cambridge, Mass.
(617) 496-7998

RELEASE: 06-192

NASA'S CHANDRA FINDS BLACK HOLES ARE 'GREEN'

Black holes are the most fuel efficient engines in the universe,
according to a new study using NASA's Chandra X-ray Observatory. By
making the first direct estimate of how efficient or "green" black
holes are, this work gives insight into how black holes generate
energy and affect their environment.

The new Chandra finding shows most of the energy released by matter
falling toward a supermassive black hole is in the form of
high-energy jets traveling at near the speed of light away from the
black hole. This is an important step in understanding how such jets
can be launched from magnetized disks of gas near the black hole's
event horizon, the distance from a black hole within which nothing,
even light, can escape.

"Just as with cars, it's critical to know the fuel efficiency of black
holes," said lead author Steve Allen of the Kavli Institute for
Particle Astrophysics and Cosmology at Stanford University and the
Stanford Linear Accelerator Center, Stanford, Calif. "Without this
information, we cannot figure out what is going on under the hood, so
to speak, or what the engine can do."

Allen and his team used Chandra to study nine supermassive black holes
at the centers of elliptical galaxies. These black holes ? from .2 to
3 billion times the mass of our sun ? are relatively old and generate
much less radiation than quasars, the rapidly growing supermassive
black holes seen in the early universe.

The surprise came when the Chandra results showed these "quiet" black
holes are all producing much more energy in jets of high-energy
particles than in visible light or X-rays. These jets create huge
bubbles, or cavities, in the hot gas in the galaxies.

The efficiency of black hole energy-production was calculated in two
steps. First, Chandra images of the galaxies' inner regions were used
to estimate how much fuel is available for the black hole. Then,
Chandra images were used to estimate the power required to produce
the cavities. The galaxies were found to produce a lot of jet power
with a surprisingly small amount of fuel.

"If a car was as fuel-efficient as these black holes, it could
theoretically travel over a billion miles on a gallon of gas," said
co-author Christopher Reynolds of the University of Maryland, College
Park.

The findings explain how black hole engines achieve this extreme
efficiency. Some of the gas first attracted to the black holes may be
blown away by the energetic activity before it gets too near the
black hole, but a significant fraction must eventually approach the
event horizon, where it is used with high efficiency to power the
jets. The study also implies that matter flows towards the black
holes at a steady rate for several million years.

"These black holes are very efficient, but it also takes a very long
time to refuel them," Allen said.

This new study also shows the energy transferred to the hot gas by the
jets should keep hot gas from cooling, thereby preventing billions of
new stars from forming. This would place limits on the growth of the
largest galaxies.

These results will appear in an upcoming issue of the Monthly Notices
of the Royal Astronomical Society. NASA's Marshall Space Flight
Center, Huntsville, Ala., manages the Chandra program for the
agency's Science Mission Directorate. The Smithsonian Astrophysical
Observatory controls science and flight operations from the Chandra
X-ray Center, Cambridge, Mass.

For additional information and images from the research, visit:

http://chandra.nasa.gov

or

http://chandra.harvard.edu/


For information about NASA and agency programs, visit:

http://www.nasa.gov/home


-end-

 




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