March 20, 2008

J.D. Harrington
Headquarters, Washington
202-358-5241
j.d.harrington@nasa.gov

Robert Naeye / Rob Gutro
Goddard Space Flight Center, Greenbelt, Md.
301-286-4453/4044

RELEASE: 08-086

NASA SATELLITE DETECTS RECORD GAMMA RAY BURST EXPLOSION HALFWAY ACROSS UNIVERSE

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 
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 Boötes. 
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

	
-end-