Steve Roy
MSFC, Huntsville, Ala.
December 12, 2002
(Phone: 256/544-0034)

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

Lobes of unexpectedly hot gas speeding away from a black hole in our galaxy
have been discovered by NASA's Chandra X-ray Observatory. The high
temperature and the distance of the lobes from the black hole indicate that
violent collisions are occurring between clumps of gas expelled from the
vicinity of the black hole.

"Just like a super-highway, it's a dangerous world out there," said Simone
Migliari on the University of Amsterdam, lead author on a paper from a
September 6, 2002 issue of Science magazine. "Blobs of gas are getting
rear-ended at speeds in excess of a hundred million miles per hours!"

The team of scientists from the University of Amsterdam and the National
Institute for Space Research (SRON) in Utrecht, The Netherlands, observed
the source SS433, a binary star system in our galaxy that consists of a
black hole and a massive star.  They detected two lobes of hot gas with
temperatures of 50 million degrees that are 0.25 light years on either side
of the black hole system. A key finding was evidence indicating rapidly
moving hot iron atoms.

The energies of the X-rays from the iron atoms in the two clouds were
shifted by the Doppler effect - the same process that causes the frequency
of an ambulance's siren to shift up and down as the ambulance approaches and
recedes.  By measuring this shift, they concluded that the lobes move away
from the vicinity of the black hole in opposite directions at a quarter of
the speed of light. The observations indicate that one lobe is moving along
a line tilted toward Earth whereas the other one is moving along a line
tilted away from Earth.

The detection of the hot gas lobes some distance away from the central black
hole was a surprise.  Earlier observations by Chandra and the Hubble Space
Telescope had shown that gas was cooling as it expanded away from the black
hole.  This led scientists to predict that no hot gas would be found further
than a few million kilometers from the black hole.

"These new observations prove that the expansion cooling model doesn't
work," said Rob Fender of the University of Amsterdam, and a coauthor on the
paper. "The gas must get reheated, most likely by high-velocity blobs
smashing into lower speed ones."

This model is also supported by long-term optical monitoring observations
that indicate that matter is ejected every few minutes in bullet-like
gaseous blobs from the vicinity of the black hole.  The bullets would travel
outward for several months without colliding until a faster bullet runs into
a slower one, precipitating a pileup that reheats the gas.  Future Chandra
observations will test this model.

The team, which also included Mariano Mendez of SRON, observed SS 433 with
the Advanced CCD Imaging Spectrometer on June 27, 2000, for a period of
9,600 seconds.  ACIS was built for NASA by Penn State, University Park, and
the Massachusetts Institute of Technology, Cambridge, Mass. NASA's Marshall
Space Flight Center, Huntsville, Ala., manages the Chandra program for the
Office of Space Science in Washington. TRW, Inc., Redondo Beach, Calif., is
the prime contractor for the spacecraft. The Smithsonian's Chandra X-ray
Center controls science and flight operations from Cambridge, Mass.

Images and additional information about this result are available at:

http://chandra.harvard.edu/
and
http://chandra.nasa.gov/

Below are links to this news release on our Web site and also to related
photos.

The Web News release
http://www1.msfc.nasa.gov/NEWSROOM/news/releases/2002/02-311.html

Photos 
http://www1.msfc. nasa.gov/ NEWSROOM/ news/photos/ 2002/photos02-311html

For releases sent directly to you, contact: judy.pettus@msfc.nasa.gov

Marshall Space Flight Center
Media Relations Department
(256) 544-0034
(256) 544-5852 (fax)
www.msfc.nasa.gov/news