Donald Savage
Headquarters, Washington, DC              December 9, 1999
(Phone:  202/358-1547)

Steve Roy
Marshall Space Flight Center, Huntsville, AL
(Phone:  256/544-6535)

Dr. Wallace Tucker
Harvard-Smithsonian Center for Astrophysics, Cambridge, MA
(Phone:  617/496-7998)

RELEASE:  99-142

CHANDRA PLOUGHS UP A SNAKE IN HYDRA A

     NASA's Chandra X-ray Observatory image of the Hydra A galaxy 
cluster has revealed a possible solution to a Herculean puzzle 
about the fate of the largest objects in the universe.

     For years astronomers have been searching unsuccessfully for 
large quantities of matter they believed must be flowing into the 
central regions of galaxy clusters.  The Chandra image of Hydra A 
displays for the first time long snake-like strands of 35 million 
degree gas extending away from the center of the cluster.  These 
structures show that the inflow of cooling gas is deflected by 
magnetic fields produced by explosions from a central black hole.

     The X-ray image also reveals a bright wedge (shown in white) 
of hot multimillion degree gas pushing into the heart of the 
cluster.  Like the legendary Hercules, who had to contend with the 
multiple heads of the monstrous Hydra, astrophysicists now know 
they must deal with the effects of magnetic fields, star 
formation, rotation and black holes if they are to understand what 
is happening in the inner regions of the galaxy cluster.

     As the largest gravitationally bound objects in the universe, 
galaxy clusters provide crucial clues for understanding the origin 
and fate of the universe.  Each large cluster such as Hydra A 
contains hundreds of galaxies and enough gaseous material to make 
a thousand more galaxies.  One intriguing question has been the 
ultimate fate of this colossal gas reservoir.   Early X-ray 
observations indicated that the gas in the inner regions of Hydra 
A should be cooling and slowly settling into the center of the 
cluster to form new galaxies or hundreds of trillions of dim 
stars.  As astronomers began searching for this cool matter, they 
were puzzled to find that the new galaxies and stars were not 
detected in sufficient numbers.

     The Chandra results on Hydra A, which is 840 million light 
years from Earth, may point to a resolution of this problem.  The 
inflow of cooling gas may be deflected by magnetic fields, and 
even pushed back into the cluster by explosions from the vicinity 
of a supermassive black hole at the core of the central galaxy.

     "In Hydra, you can see the whole cycle," said Brian McNamara 
of the Harvard-Smithsonian Center for Astrophysics.  "You have the 
hot gas cloud, the disk of material feeding the black hole, and 
the evidence that the explosion from the gas near the black hole 
is pushing the hot gas around."

     Indeed, combined radio and X-ray observations suggest that a 
vast bubble of high energy particles is pushing the hot gas aside, 
creating the Hydra-like loops of hot gas.  Similar processes are 
likely to be at work in other galaxy clusters, and in newly 
forming galaxies that are collapsing from a cloud of gas.  By 
using images with Chandra and other telescopes, astronomers may 
eventually conquer a "monstrous" problem of cosmic significance.

     The Chandra image was taken with the Advanced CCD Imaging 
Spectrometer (ACIS) on October 30, 1999, in an observation that 
lasted about six hours.

     High resolution digital versions of the X-ray image (JPG, 300 
dpi TIFF) and other information associated with this release are 
available on the Internet at:

                http://chandra.harvard.edu/photo/0087/ 

                         or through links at:

                       http://chandra.nasa.gov

      NASA's Marshall Space Flight Center, Huntsville, AL, manages 
the Chandra program.  TRW, Inc., Redondo Beach, CA, is the prime 
contractor for the spacecraft.  The Smithsonian's Chandra X-ray 
Center controls science and flight operations from Cambridge, MA.

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