Trent J. Perrotto
Headquarters, Washington
202-358-0321
trent.j.perrotto@nasa.gov
Megan Watzke
Chandra X-ray Center, Cambridge, Mass.
617-496-7998
mwatzke@cfa.harvard.edu
RELEASE: 11-247
NASA'S CHANDRA OBSERVATORY IMAGES GAS FLOWING TOWARD BLACK HOLE
WASHINGTON -- The flow of hot gas toward a black hole has been clearly
imaged for the first time in X-rays. The observations from NASA's
Chandra X-ray Observatory will help tackle two of the most
fundamental problems in modern astrophysics: understanding how black
holes grow and how matter behaves in their intense gravity.
The black hole is at the center of a large galaxy known as NGC 3115,
which is located about 32 million light years from Earth. A large
amount of previous data has shown material falling toward and onto
black holes, but none with this clear a signature of hot gas.
By imaging the hot gas at different distances from this supermassive
black hole, astronomers have observed a critical threshold where the
motion of gas first becomes dominated by the black hole's gravity and
falls inward. This distance from the black hole is known as the
"Bondi radius."
"It's exciting to find such clear evidence for gas in the grip of a
massive black hole," said Ka-Wah Wong of the University of Alabama,
who led the study that appears in the July 20th issue of The
Astrophysical Journal Letters. "Chandra's resolving power provides a
unique opportunity to understand more about how black holes capture
material by studying this nearby object."
As gas flows toward a black hole, it becomes squeezed, making it
hotter and brighter, a signature now confirmed by the X-ray
observations. The researchers found the rise in gas temperature
begins about 700 light years from the black hole, giving the location
of the Bondi radius. This suggests the black hole in the center of
NGC 3115 has a mass about two billion times that of the sun, making
it the closest black hole of that size to Earth.
The Chandra data also show the gas close to the black hole in the
center of the galaxy is denser than gas further out, as predicted.
Using the observed properties of the gas and theoretical assumptions,
the team then estimated that each year gas weighing about 2 percent
the mass of the sun is being pulled across the Bondi radius toward
the black hole.
Making certain assumptions about how much of the gas's energy changes
into radiation, astronomers would expect to find a source that is
more than a million times brighter in X-rays than what is seen in NGC
3115.
"A leading mystery in astrophysics is how the area around massive
black holes can stay so dim, when there's so much fuel available to
light up," said co-author Jimmy Irwin, also of the UA in Tuscaloosa.
"This black hole is a poster child for this problem."
There are at least two possible explanations for this discrepancy. The
first is that much less material actually falls onto the black hole
than flows inside the Bondi radius. Another possibility is that the
conversion of energy into radiation is much less efficient than is
assumed.
Different models describing the flow of material onto the black hole
make different predictions for how quickly the density of the gas is
seen to rise as it approaches the black hole. A more precise
determination of the rise in density from future observations should
help astronomers rule out some of these models.
NASA's Marshall Space Flight Center in Huntsville, Ala., manages the
Chandra program for the agency's Science Mission Directorate in
Washington. The Smithsonian Astrophysical Observatory controls
Chandra's science and flight operations from Cambridge, Mass.
More information, including images and other multimedia, can be found
at:
and
-end-
To subscribe to the list, send a message to:
hqnews-subscribe@mediaservices.nasa.gov
To remove your address from the list, send a message to:
hqnews-unsubscribe@mediaservices.nasa.gov
No comments:
Post a Comment