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Nancy Neal
Headquarters, Washington            March 31, 2003
(Phone: 202/358-2369)

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

Deborah Halber
Massachusetts Institute of Technology, Cambridge, Mass.
(Phone: 617/258-9276)

RELEASE: 03-126

NASA DETECTS ONE OF CLOSEST AND BRIGHTEST GAMMA RAY BURSTS

     The Universe clearly works weekends; delivering one of 
the brightest and closest gamma ray bursts yet on Saturday, 
March 29, at 6:37 a.m. EST. 

NASA's High-Energy Transient Explorer (HETE) detected the 
burst, signaling the birth of a black hole, in the 
constellation Leo. For more than 30 seconds, the burst out 
shone the entire Universe in gamma rays, and its afterglow 
was still over a trillion times brighter than the sun two 
hours later. This was the brightest burst yet detected by 
HETE and is in the top one percent of all bursts in terms of 
intrinsic brightness. Within seconds, HETE nailed down a 
location and subsequently relayed the coordinates to the 
astronomy community, allowing hundreds of scientists and 
amateur astronomers to join the observation, from Australia 
to Finland and across the ocean to America. Observations 
continue to pour in as scientists attempt to unravel what 
caused the burst. The region is still too bright to determine 
which galaxy this burst came from. 

"This was our biggest one ever, and it didn't get away," said 
Dr. George Ricker of the Massachusetts Institute of 
Technology (MIT), Cambridge, Mass., and principal 
investigator for the HETE mission. "With scores of 
observations now completed and more on the way, we should get 
a rather clear picture of what triggered this burst." 

Gamma ray bursts are the most powerful explosions in the 
Universe; likely caused by the death of a massive star, in 
which the core implodes to form a black hole. Bursts appear 
to occur randomly, and few last more than a minute, making 
them hard to study.

HETE detects the fleeting gamma ray and X-ray portions of 
these bursts, and its prompt localization enables scientists 
to study the burst afterglow, which can linger from days to 
weeks in optical light and radio waves. Most bursts originate 
in the early universe, traveling upwards of 10 billion years 
at light speed to reach us. 

The burst on March 29 was named GRB 030329. Both the burst 
and its afterglow were brilliant. The burst poured out a 
thousand trillion, trillion times the gamma rays seen in a 
solar flare. When measured more than one hour after the 
burst, the afterglow was still about as bright as a 12th 
magnitude star. This means it was only about 10 to 100 times 
dimmer than what can be seen with the naked eye, visible with 
backyard telescopes. At its peak, the afterglow may have been 
visible to the naked eye. 

The burst originated approximately two billion light years 
from Earth, which is relatively close. The GRB 030329 
redshift measurement was 0.168, making this the second 
closest burst with a known redshift measurement. (Redshift is 
a measurement of how light from distant regions of the 
Universe is "shifted" to lower energy as the Universe 
expands; the greater the redshift, the greater the distance 
from Earth.)  "Few amateur astronomers are treated to an 
event that originated billions of light years away," said 
Ricker.

Bruce Peterson and Paul Price of the Research School of 
Astronomy and Astrophysics at the Australian National 
University, Canberra, first identified the burst afterglow. 
An automated telescope at Japan's RIKEN science institute 
quickly confirmed the location. Finnish amateur astronomers 
provided even tighter constraints on the properties of the 
afterglow. Multiple observations enable a thorough study of 
the burst environment. 

Gamma ray burst hunters are aided by three new developments: 
fast triggers from orbiting detectors; fast relays to 
observers worldwide via the Gamma ray burst Coordinates 
Network (GCN); and fast responses from ground-based robotic 
telescopes. HETE is the first satellite to provide and 
distribute accurate burst locations within seconds. 

The GCN, developed and maintained at NASA's Goddard Space 
Flight Center in Greenbelt, Md., serves as a gamma ray burst 
hub. HETE signals the GCN, which sends out "phone calls" and 
email messages to scientists and amateurs worldwide. The GCN 
Web site also posts scientific information from the 
astronomers making observations. 

HETE was built by MIT as a mission of opportunity under the 
NASA Explorer Program, with collaboration among U.S. 
universities, Los Alamos, N.M. National Laboratory, 
scientists and organizations in Brazil, France, India, Italy 
and Japan. To track the progress of GRB 030329 and to learn 
more about the HETE mission on the Internet, visit:

http://gcn.gsfc.nasa.gov
http://space.mit.edu/HETE/

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