On 2008 Sept. 17, 31.7 hours after GRB 080916C exploded, the MPE Gamma-Ray Burst
Optical/Near-Infrared Detector (GROND) on the 2.2m Max Planck Telescope
at the European Southern Observatory, La Silla, Chile, began acquiring
images of the blast's fading afterglow (circled).
Image: MPE / GROND
NASA'S FERMI TELESCOPE SEES MOST EXTREME GAMMA-RAY BLAST YET
The first gamma-ray burst to be seen with substantial GeV emission from
NASA's Fermi Gamma-ray Space Telescope is one for the record books. The
blast had the greatest total energy, the fastest motions and the
highest-energy initial emissions ever seen.
This explosion, designated GRB 080916C, occurred at 0:13 UT on
2008 Sept. 16, in the constellation Carina. Fermi's other instrument, the
Gamma-ray Burst Monitor, simultaneously recorded the event. Together,
the two instruments provide a view of the blast's initial, or prompt,
gamma-ray emission from energies between 3,000 to more than 5 billion
times that of visible light.
Nearly 32 hours after the blast, Jochen Greiner of the Max Planck Institute
for Extraterrestrial Physics in Garching, Germany, led a group that
searched for the explosion's fading afterglow. The team simultaneously
captured the field in seven wavelength bands using the MPE built and
operated detector GROND.
In certain colors, the brightness of a distant object shows a characteristic
drop-off caused by intervening gas clouds. The farther away the object
is, the redder the wavelength where this fade-out occurs. This gives
astronomers a quick estimate of the object's distance. The team's follow-up
observations established that the explosion took place 12.2 billion
"Already, this was an exciting burst," said Julie McEnery, a Fermi deputy
project scientist at NASA's Goddard Space Flight Center in Greenbelt, Md.
"But with the GROND team's distance, it went from exciting to extraordinary."
The Fermi team's results appeared for the first time on February 19, 2009
in the online edition of the journal Science.
The GROND results will be published in Astronomy & Astrophysics.