Extreme Gamma-ray Burst

The first gamma-ray burst to be seen in high-resolution 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.

The first gamma-ray burst to be seen in high-resolution 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 7:13 p.m. EDT on Sept. 15, 2008, in the constellation Carina. This movie compresses about 8 minutes of Fermi LAT observations of GRB 080916C into 6 seconds. Colored dots represent gamma rays of different energies:

Above: A Fermi LAT movie of the extreme gamma-ray burst. The blue dots represent lower-energy gamma rays (less than 100 million eV); green, moderate energies (100 million to 1 billion eV); and red, the highest energies (more than 1 billion eV). Credit: NASA/DOE/Fermi LAT Collaboration. [Quicktime video]

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, a group led by Jochen Greiner of the Max Planck Institute for Extraterrestrial Physics in Garching, Germany, found the afterglow of GRB 080916C. Working quickly, before it could fade away, they measured the afterglow’s spectrum using the Gamma-Ray Burst Optical/Near-Infrared Detector, or GROND, on the 2.2-meter telescope at the European Southern Observatory in La Silla, Chile.

With the distance in hand, Fermi team members calculated that the blast exceeded the power of approximately 9,000 ordinary supernovae, if the energy was emitted equally in all directions. This is a standard way for astronomers to compare events even though gamma-ray bursts emit most of their energy in tight jets.

Coupled with the Fermi measurements, the distance also helps astronomers determine the speed of the gamma-ray emitting material. Within the jet of this burst, gas bullets must have moved at least 99.9999 percent the speed of light. This burst’s tremendous power and speed make it the most extreme recorded to da

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