Scientists have discovered one of the brightest and
closest gamma ray bursts on record is also a supernova.
Scientists obtained the first direct evidence linking these
two types of explosions, both triggered by the death of a
massive star.
NASA’s High-Energy Transient Explorer satellite (HETE)
initially detected the burst on March 29, 2003, in the
constellation Leo. For more than 30 seconds, the burst
outshone the entire universe in gamma rays, and its optical
afterglow was still more than a trillion times brighter than
the sun two hours later.
Through observations of the gamma ray burst afterglow,
astronomers spotted the telltale signs of a supernova.
Scientists cannot yet determine which came first, the burst
or the supernova, but the same event, a star explosion, was
certainly the trigger for both.
“There should no longer be doubt in anybody’s mind that
gamma ray bursts and supernovae are connected,” said Dr.
Thomas Matheson of the Harvard-Smithsonian Center for
Astrophysics (CfA), Cambridge, Mass., and a member of the
team that made the discovery.
Matheson’s colleagues include Dr. Peter Garnavich of Notre
Dame and Dr. Krzysztof Stanek of the CfA. Nearly two-dozen
scientists, primarily using the Multiple Mirror Telescope
(MMT) at Mount Hopkins, Ariz., obtained the data. When the
burst was discovered, astronomers scheduled to use the MMT
agreed to observe it as a target of opportunity in
collaboration with Garnavich, Matheson and Stanek.
Gamma ray bursts are the most powerful explosions in the
universe, and they likely signal the birth of black holes.
Bursts occur at random locations scattered across the sky.
Few last more than a minute, making them hard to study.
A supernova is the explosion of a star at least eight times
as massive as the sun. When such stars deplete their nuclear
fuel, they no longer have the energy to support their mass.
Their cores implode, forming either a neutron star or, if
there is enough mass, a black hole. The surface layers of
the star blast outward, forming the colorful patterns
typical of supernova remnants.
Previous observations, particularly from NASA’s Chandra X-
ray Observatory, have provided convincing indirect evidence
of the gamma ray burst/supernova connection. The Chandra
Observatory detected iron and other heavy elements, which
are formed in supernovae, in the vicinity of gamma ray
bursts.
Matheson and the others detected direct evidence the burst
afterglow’s light is exhibiting the same patterns as light
from a supernova. Namely, the scientists see changes in
light absorbed by silicon and iron atoms, forged in the
supernova, as the afterglow slowly fades away. The team is
continuing to observe and analyze this unique burst.
“Scores of observatories, and even more observers, are now
studying this event,” said Dr. Donald Kniffen, at NASA
Headquarters in Washington. “We’ve been searching for a
direct link for decades, and we finally got it,” he said.
“All gamma ray bursts may have associated supernovae that
are too faint to observe,” Matheson said. The March 29
burst, named GRB 030329, was one of the closest to Earth. It
was approximately two billion light-years away, as opposed
to other bursts located more than 10 billion light-years
away. Because the burst was both relatively close to Earth
and bright, the supernova was detectable.
The Massachusetts Institute of Technology in Cambridge,
Mass., 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,
built HETE.
For more information about NASA, HETE and CfA on the
Internet, visit:
