Steve Roy

Media Relations Department

(256) 544-0034

RELEASE: 00-008

Astronomers End Year with a Bang: NASA Uses Teamwork to Learn about One of the Most Powerful Explosions in the Universe

Scientists from around the world have taken advantage of NASA teamwork to quickly locate
and observe a gamma ray burst — one of the most violent events in the universe.

Astronomers pinpointed the precise location of the blast on Dec. 16, 1999, by using
coordinated observations from the Burst and Transient Source Experiment (BATSE)
managed by NASA’s Marshall Space Flight Center in Huntsville, Ala., and the Rossi X-ray
Timing Explorer operated by NASA’s Goddard Space Flight Center in Greenbelt, Md.

“This is the first major success in using instruments on two NASA satellites to locate a
burst quickly,” said Dr. Marc Kippen, a University of Alabama in Huntsville astrophysicist
working on the BATSE team at the Marshall Center.

It can take several hours to reprogram a spacecraft to point to a source. By then the
afterglow left by the burst explosion is usually too faint to be detected. That is why Marshall’s
Burst Experiment, designed specifically to detect elusive gamma ray bursts, is usually the
first — and sometimes only — instrument to detect these mysterious explosions.

The Burst Experiment apparatus includes eight detector modules mounted on the corners
of NASA’s Compton Gamma Ray Observatory orbiting Earth. BATSE’s ability to see gamma
ray bursts across most of the universe has given scientists the most information ever
obtained on bursts. But the detectors’ ability to see gamma ray bursts across most of the
universe reduces their precision in determining burst locations.

To locate bursts more accurately, Marshall’s BATSE team worked with the Rossi Explorer
team to develop a way to get information to the Rossi satellite so that it could quickly aim
toward the burst and record information before the explosion’s glow faded. Rossi pointed
toward the burst and recorded data within four hours of the burst.

“We determined the burst location so precisely and so quickly that we had enough time to
send information to other telescopes, like the Chandra X-ray Observatory,” said Kippen.
“These bigger observatories need more precise information and even more time to aim at a
burst. Usually by the time we have enough data on a burst’s location, it has already faded
and can’t be seen by other observatories.”

NASA’s space-based Chandra Observatory, managed by the Marshall Center, was able to
swing into position and catch the fading embers of the burst four days after the explosion,
providing data on X-rays released by the blast.

Other observatories in space and on the ground recorded the energy being released from
the blast in the form of gamma rays, X-rays and visible and radio waves. Using a variety of
spacecraft to record different signatures of visible and invisible energy will enable scientists
to learn more about these mysterious explosions.

“It was an excellent opportunity for Chandra to make its first observation of a gamma-ray
source,” said Dr. Gerald Fishman, principal investigator for the Burst and Transient Source
Experiment at the Marshall Center. “The coordinated effort shows the value of spacecraft
and people working together to make exciting observations that could not be made by one
single observatory.”

The reward for the years of effort to obtain this set of complementary observations is the
large volume of data obtained on the burst. One early result has been published in
astronomical circulars, indicating the blast occurred more than 10 billion light years away —
putting it, in terms of age, roughly 2 billion years after the “Big Bang.” A light year is the
distance light travels in one year. The Big Bang theory assumes that initially the universe
existed as a single compact ball of matter that exploded, forming gaseous debris, which
eventually condensed to form stars and galaxies.

Scientists expect to publish many more findings about this burst in journals. The burst —
which one astronomer nicknamed Beethoven because it fell on the anniversary of the
composer’s birth on Dec. 16, 1770 — was one of the brightest ever recorded by BATSE. The
burst’s official name is GRB 991216.

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