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


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:

or through links at:

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.

– end –