NASA Satellite Detects Record Gamma Ray Burst Explosion Halfway Across Universe
March 20 2008 - 6:07PM
PR Newswire (US)
WASHINGTON, March 20 /PRNewswire-USNewswire/ -- 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 bang. "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 Bootes. 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. For related images to this
story, visit: http://www.nasa.gov/swift DATASOURCE: NASA CONTACT:
J.D. Harrington, Headquarters, Washington, +1-202-358-5241, , or
Robert Naeye, +1-301-286-4044, Rob Gutro, +1-301-286-4453, Goddard
Space Flight Center, Greenbelt, Md., all of NASA Web Site:
http://www.nasa.gov/
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