Thursday, March 20, 2008

19 March 08 Gamma Ray Burst

It might be interested to look through the SID data for this:

-------- Original Message --------
Subject: NASA Satellite Detects Record Gamma Ray Burst Explosion Halfway Across Universe
Date: Thu 20 Mar 2008 18:10:00 EDT
From: NASA News
To: NASA News

March 20, 2008

J.D. Harrington
Headquarters, Washington

Robert Naeye / Rob Gutro
Goddard Space Flight Center, Greenbelt, Md.

RELEASE: 08-086


WASHINGTON - A powerful stellar explosion detected March 19 by NASA's
Swift satellite has shattered the record for the most distant object
that could be seen with the naked eye.

The explosion was a gamma ray burst. Most gamma ray bursts occur when
massive stars run out of nuclear fuel. Their cores collapse to form
black holes or neutron stars, releasing an intense burst of
high-energy gamma rays and ejecting particle jets that rip through
space at nearly the speed of light like turbocharged cosmic
blowtorches. When the jets plow into surrounding interstellar clouds,
they heat the gas, often generating bright afterglows. Gamma ray
bursts are the most luminous explosions in the universe since the big

"This burst was a whopper," said Swift principal investigator Neil
Gehrels of NASA's Goddard Space Flight Center in Greenbelt, Md. "It
blows away every gamma ray burst we've seen so far."

Swift's Burst Alert Telescope picked up the burst at 2:12 a.m. EDT,
March 19, and pinpointed the coordinates in the constellation Bo?tes.
Telescopes in space and on the ground quickly moved to observe the
afterglow. The burst is named GRB 080319B, because it was the second
gamma ray burst detected that day.

Swift's other two instruments, the X-ray Telescope and the
Ultraviolet/Optical Telescope, also observed brilliant afterglows.
Several ground-based telescopes saw the afterglow brighten to visual
magnitudes between 5 and 6 in the logarithmic magnitude scale used by
astronomers. The brighter an object is, the lower its magnitude
number. From a dark location in the countryside, people with normal
vision can see stars slightly fainter than magnitude 6. That means
the afterglow would have been dim, but visible to the naked eye.

Later that evening, the Very Large Telescope in Chile and the
Hobby-Eberly Telescope in Texas measured the burst's redshift at
0.94. A redshift is a measure of the distance to an object. A
redshift of 0.94 translates into a distance of 7.5 billion light
years, meaning the explosion took place 7.5 billion years ago, a time
when the universe was less than half its current age and Earth had
yet to form. This is more than halfway across the visible universe.

"No other known object or type of explosion could be seen by the naked
eye at such an immense distance," said Swift science team member
Stephen Holland of Goddard. "If someone just happened to be looking
at the right place at the right time, they saw the most distant
object ever seen by human eyes without optical aid."

GRB 080319B's optical afterglow was 2.5 million times more luminous
than the most luminous supernova ever recorded, making it the most
intrinsically bright object ever observed by humans in the universe.
The most distant previous object that could have been seen by the
naked eye is the nearby galaxy M33, a relatively short 2.9 million
light-years from Earth.

Analysis of GRB 080319B is just getting underway, so astronomers don't
know why this burst and its afterglow were so bright. One possibility
is the burst was more energetic than others, perhaps because of the
mass, spin, or magnetic field of the progenitor star or its jet. Or
perhaps it concentrated its energy in a narrow jet that was aimed
directly at Earth.

GRB 080319B was one of four bursts that Swift detected, a Swift record
for one day. "Coincidentally, the passing of Arthur C. Clarke seems
to have set the universe ablaze with gamma ray bursts," said Swift
science team member Judith Racusin of Penn State University in
University Park, Pa.

Swift is managed by Goddard. It was built and is being operated in
collaboration with Penn State, the Los Alamos National Laboratory,
and General Dynamics in the U.S.; the University of Leicester and
Mullard Space Sciences Laboratory in the United Kingdom; Brera
Observatory and the Italian Space Agency in Italy; plus partners in
Germany and Japan.

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