Nancy Neal
Headquarters, Washington
(Phone: 202/358-2369)
Bill Steigerwald
Goddard Space Flight Center, Greenbelt, Md.
(Phone: 301/286-5017)
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/