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recently, little had been known about the "fireballs" known
as gamma ray bursts. Since their discovery about 30 years ago by defense
satellites, these intense cosmic outbursts seem to occur randomly around
the sky about once per day.
In 1997, a team of astronomers using a pair of NSF radio telescopes made
the first measurements of the size and expansion of gamma ray bursts.
These scientists have learned the fireball is actually debris
that expands at very nearly the speed of light.
In these events enormous amounts of energy are released
within a very small region which is considered much less than the typical
distance separating stars.
cause of gamma ray bursts is still unknown.
One burst in 1997 lasted for only 15 seconds, but emitted an afterglow
that lasted for several days. Study of the afterglow reveals the initial
explosion released more energy during 15 seconds
than the sun will release in its entire 10-billion year lifetime, making
it one of the most energetic events known to have occurred since the Big
Optical studies reveal the 1997 gamma ray burst was at least seven billion
light-years away. Because
of their short duration, gamma ray bursts are difficult to "catch."
are devising clever techniques in order to learn the cause, frequency
and role these events play in the evolution of the universe.