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Interesting Astronomy News

May 07, 1998 09:43 AM
by Eldon B Tucker

The idea of such a big burst of energy is
something new. Makes one wonder how it fits
in with the theosophical cosmology ...

-- Eldon

---- from a NASA web page ---

Donald Savage
Headquarters, Washington, DC                           May 6, 1998
(Phone:  202/358-1547)                  EMBARGOED UNTIL 2 P.M. EDT

Bill Steigerwald
Goddard Space Flight Center, Greenbelt, MD
(Phone:  301/286-5017)

Robert Tindol
California Institute of Technology, Pasadena, CA
(Phone:  626/395-3631)

RELEASE:  98-75


       A recently detected cosmic gamma ray burst released a
hundred times more energy than previously theorized, making it the
most powerful explosion since the creation of the universe in the
Big Bang.

       "For about one or two seconds, this burst was as luminous
as all the rest of the entire universe," said Caltech professor
George Djorgovski, one of the two principal investigators on the
team from the California Institute of Technology, Pasadena, CA.

       The team measured the distance to a faint galaxy from which
the burst originated at about 12 billion light years from the
Earth.  The observed brightness of the burst despite this great
distance implies an enormous energy release.  The team's findings
appear in the May 7 issue of the journal Nature.

       The burst was detected on Dec. 14, 1997, by the
Italian/Dutch BeppoSAX satellite and NASA's Compton Gamma Ray
Observatory satellite.  The Compton observatory provided detailed
measurements of the total brightness of the burst, designated GRB
971214, while BeppoSAX provided its precise location, enabling
follow-up observations with ground-based telescopes and NASA's Hubble Space

       "The energy released by this burst in its first few seconds
staggers the imagination," said Caltech professor Shrinivas
Kulkarni, the other principal investigator on the team.

       The burst appears to have released several hundred times
more energy than an exploding star, called a supernova, until now
the most energetic known phenomenon in the universe.  Finding such
a large energy release over such a brief period of time is
unprecedented in astronomy, except for the Big Bang itself.

       "In a region about a hundred miles across, the burst
created conditions like those in the early universe, about one
millisecond (1/1,000 of a second) after the Big Bang," said

       This large amount of energy was a surprise to astronomers.
"Most of the theoretical models proposed to explain these bursts
cannot explain this much energy," said Kulkarni.  "However, there
are recent models, involving rotating black holes, which can work.
On the other hand, this is such an extreme phenomenon that it is
possible we are dealing with something completely unanticipated
and even more exotic."

       Gamma-ray bursts are mysterious flashes of high-energy
radiation that appear from random directions in space and
typically last a few seconds.  They were first discovered by U.S.
Air Force Vela satellites in the 1960s.  Since then, numerous
theories of their origin have been proposed, but the causes of
gamma-ray bursts remain unknown.  The Compton observatory has
detected several thousand bursts so far.

       The principal limitation in understanding the bursts was
the difficulty in pinpointing their direction on the sky.  Unlike
visible light, gamma rays are exceedingly difficult to observe
with a telescope, and the bursts' short duration exacerbates the
problem.  With BeppoSAX, scientists now have a tool to localize
the bursts on the celestial sphere with sufficient precision to
permit follow-up observations with the world's most powerful
ground-based telescopes.

       This breakthrough led to the discovery of long-lived
"afterglows" of bursts in X-rays, visible and infrared light, and
radio waves.  While gamma-ray bursts last only a few seconds,
their afterglows can be studied for several months.  Study of the
afterglows indicated that the bursts do not originate within our
own galaxy, the Milky Way, but rather are associated with
extremely distant galaxies.

       Both BeppoSAX and NASA's Rossi X-ray Timing Explorer
spacecraft detected an X-ray afterglow.  BeppoSAX precision led to
the detection of a visible light afterglow, found by a team from
Columbia University, New York, NY, and Dartmouth College, Hanover,
NH, including Professors Jules Halpern, David Helfand, John
Torstensen, and their collaborators, using a 2.4-meter telescope
at Kitt Peak, AZ, but no distance could be measured from these

       As the visible light from the burst afterglow faded, the
Caltech team detected an extremely faint galaxy at its location,
using one of the world's largest telescopes, the 10-meter Keck II
telescope at Mauna Kea, Hawaii.  The galaxy is about as faint as
an ordinary 100 watt light bulb would be as seen from a distance
of a million miles.

       Subsequent images taken with the Hubble Space Telescope
confirmed the association of the burst afterglow with this faint
galaxy and provided a more detailed image of the host galaxy.

       The Caltech team succeeded in measuring the distance to
this galaxy, using the light-gathering power of the Keck II
telescope.  The galaxy is at a redshift of z=3.4, or about 12
billion light years distant (assuming the universe to be about 14
billion years old).

       From the distance and the observed brightness of the burst,
astronomers derived the amount of energy released in the flash.
Although the burst lasted approximately 50 seconds, the energy
released was hundreds of times larger than the energy given out in
supernova explosions, and it is about equal to the amount of
energy radiated by our entire Galaxy over a period of a couple of
centuries.  Scientists say it is possible that other forms of
radiation from the burst, such as neutrinos or gravity waves,
which are extremely difficult to detect, carried a hundred times
more energy than that.

       NASA is planning two missions to further investigate gamma-
ray bursts:  the High Energy Transient Experiment II (HETE II),
scheduled to launch in the fall of 1999, and the Gamma Ray Large
Area Space Telescope (GLAST), scheduled to launch in 2005.  HETE
II will be able to precisely locate gamma-ray bursts in near real-
time and quickly transmit their locations to ground-based

observatories, permitting rapid follow-up studies.  GLAST will
detect only those gamma-ray bursts that emit the highest energy
gamma rays, and will be able to locate them with sufficient
precision to permit coordinated observations from the ground.
Because not much is known about the bursts at these high energies,
the observations may permit researchers to choose among competing
theories for the origin of gamma-ray bursts.

                           - end -

NOTE TO EDITORS:   Images of the GRB 971214 field are available
Information on the BeppoSAX spacecraft is available at:
Information on the Compton Gamma Ray Observatory is available at:
Information on Gamma Ray Bursts is available at:

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