RACE TO GAMMA RAY BURST REVEALS GIGANTIC EXPLOSION, DEATH, & BIRTH

Nancy Neal
Headquarters, Washington           March 19, 2003
(Phone: 202/358-2369)

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

RELEASE: 03-107

RACE TO GAMMA RAY BURST REVEALS GIGANTIC EXPLOSION, DEATH, & 
BIRTH

     Scientists arriving on the scene of a gamma ray burst, 
just moments after the explosion, have witnessed the death 
of a gigantic star and the birth of something monstrous in 
its place, quite possibly a brand-new, spinning black hole. 

The burst observation, featured in the March 20 issue of 
Nature, is the most detailed to date. The observation 
confirms gamma ray bursts announce the demise of the most 
massive stars in the universe, a theory called the 
"collapsar model." NASA's High-Energy Transient Explorer 
(HETE), ground-based robotic telescopes, and fast-thinking 
researchers around the globe, made the timely observation 
possible. 

"This stunning observation places us in the fiery throes of 
a star explosion, peering through the debris at a newly 
formed black hole within," said Dr. Anne Kinney, NASA 
director for astronomy and physics, Headquarters, 
Washington.

"If a gamma ray burst is the birth cry of a black hole, then 
the HETE satellite has just allowed us into the delivery 
room," said Dr. Derek Fox of the California Institute of 
Technology in Pasadena, Calif., the lead author of the 
Nature paper.

Gamma ray bursts shine hundreds of times brighter than a 
supernova, or as bright as a million trillion suns. The 
mysterious bursts are common, yet random and fleeting. The 
gamma ray portion of a burst typically lasts from a few 
milliseconds to 100 seconds. An afterglow, caused by shock 
waves from the explosion sweeping up matter and ramming this 
into the region around the burst, can linger for days or 
weeks in lower-energy forms of light, such as X-rays or 
visible light. 

A gamma ray burst, named GRB021004, appeared on October 4, 
2002, at 8:06 a.m. EDT. Wasting no time, HETE spotted the 
burst, nailed down a location, and notified observers 
worldwide within a few seconds, while the gamma rays were 
still pouring in. First on the scene was the Automated 
Response Telescope (ART) in Wako, Japan, observing the 
region just 193 seconds after the burst. 

Fox pinpointed the afterglow shortly after this from images 
captured by a telescope on Mt. Palomar, near San Diego. Then 
the race was on, as scientists, using more than 50 
telescopes, in California, across the Pacific, Australia, 
Asia and Europe zoomed in on the afterglow before the 
approaching sunrise. 

Scientists arrived on the scene of GRB021004 early enough to 
witness an entirely new phenomenon: the ongoing energizing 
of the burst afterglow for more than half an hour after the 
burst. This power must have been provided by whatever object 
produced the gamma ray burst itself. 

"Gamma ray bursts must be many times more times powerful 
than we previously thought," said Dr. George Ricker of the 
Massachusetts Institute of Technology (MIT), Cambridge, 
Mass., principal investigator for the HETE mission. "The 
gamma-ray portion of the burst is perhaps just the tip of 
the iceberg," he said. 

These findings support the collapsar model, where the core 
of a massive star collapses into a black hole. The black 
hole's spin or magnetic fields may be acting like a 
slingshot, flinging material into the surrounding debris. 
Scientists calculated GRB021004 originated from a star 15 
times more massive than Earth's sun. 

Gamma ray burst hunters are greatly aided by three new 
developments: fast triggers from orbiting detectors; fast 
relays to observers worldwide via the Gamma ray burst 
Coordinates Network; and fast responses from ground-based 
robotic telescopes. HETE is the first satellite to provide 
and distribute accurate burst locations within seconds. In 
December 2003, NASA will launch the Swift satellite, which 
will have an even greater capability to detect and locate 
bursts, as well as onboard optical, ultraviolet and X-ray 
telescopes. 

Fox and his colleagues relied on data from ART in Japan, the 
Palomar Oschin Telescope, and the Near Earth Asteroid 
Tracking camera, which are automated. HETE was built by MIT 
as a mission of opportunity under the NASA Explorer Program, 
collaboration among U.S. universities, Los Alamos National 
Laboratory in New Mexico, scientists and organizations in 
Brazil, France, India, Italy and Japan. 

For high-quality animation and more information about the 
HETE program, refer to:


http://www.gsfc.nasa.gov/topstory/2003/0319hete.html
http://space.mit.edu/HETE/