Sue Hartigan <[EMAIL PROTECTED]> writes:
WASHINGTON, May 6 (UPI) _ Astronomers report they have witnessed the
largest explosion
ever recorded in the universe, and may rival most other releases of
energy since the big bang.
In the space of a few seconds, the far-distant, mysterious explosion
hurled out more than 100 times
the energy the sun will emit during its entire 10-billion-year lifetime.
Shri Kulkarni, the leader of one of several teams that have analyzed the
discovery, says even space
scientists used to thinking in universe- scale numbers find that energy
``mind-boggling.''
Kulkarni's California Institute of Technology team and another based at
Columbia University
present their findings in Thursday's issue of the British journal Nature
and at a press briefing
Wednesday at NASA headquarters in Washington.
The explosion is called a gamma-ray burst, a phenomenon known since the
1950s. Two features of
this discovery in particular, however, are likely to force scientists to
redefine previous theories about
origin of these bursts:
_First, its almost unimaginable energy. Gamma Ray Burst 971214, named
after the date last
December when it occurred, was hundreds of times more powerful than
scientists predicted
possible. In its lifetime, estimated at two to 10 seconds, the gamma ray
burst emitted energy roughly
equal to that generated in a similar short period by all 10 billion
trillion stars in the entire universe.
_Second, its distance. The burst occurred about 12 billion light- years
away. A light year is the
distance light travels in a vacuum in a year, or 5.88 trillion miles
(9.46 trillion kilometers). Only last
year did the Caltech team definitively prove that gamma-ray bursts come
from outside the Milky
Way galaxy, which is only about 100,000 light-years across.
The two features _ energy and distance _ are actually related, says
astronomer Charles Meegan of
NASA's Marshall Space Flight Center. The Huntsville, Ala.-based expert
points out that ``you'd
have to hold a light bulb awfully close to your eye before it started
looking as bright as the sun.''
Meegan says of the discovery, ``Realizing now how powerful and distant
these bursts are is like
when people realized that the points of light in the night sky were
really stars like our own sun.''
Pinpointing these bursts is a recent accomplishment because gamma rays
are so powerful they
simply pass through a telescope's mirror like sunlight passes through
window glass. The explosion
itself is also over in a matter of seconds.
GRB971214 was first captured by the Italian-Dutch satellite called
BeppoSAX, which for the first
time can at least narrow down the location of a gamma-ray burst to a
region of space smaller than
the size the moon.
David Helfand of Columbia University received the alert from Rome at
11:15 p.m. on a Sunday
night last December.
He told United Press International, ``It was probably the first time
I've been in my office at that hour
in 20 years. If I hadn't been there, we would have missed it.''
He quickly called colleagues at the Kitt Peak Observatory in Tucson,
Ariz., who happened to have
a camera attached to the 2.4-meter telescope that night.
Over the next two nights, infrared images revealed an object in the
constellation Ursa Major that
was quickly fading.
As the burst's energy receded, Kulkarni's team at Mauna Kea, Hawaii,
began to see a very faint,
fuzzy body. The huge light-gathering ability of the 10-meter Keck II
telescope had found ``not just a
star-light object, but a host galaxy at the exact position,'' Kulkarni
says.
With the explosion's source in sight, the Caltech team could calculate
its distance, and thus energy.
NASA's Compton Gamma-Ray Observatory spacecraft, which detected
GRB971214, has picked
up about 2,000 gamma-ray bursts so far. The phenomenon was unknown until
military satellites,
launched to monitor nuclear testing in the 1950s, detected the bursts.
They had not been observed
before that, because the Earth's atmosphere blocks gamma rays.
--
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1. Don't tell people everything you know.
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