NASA’s Fermi Telescope Sees Most Extreme Gamma-Ray Blast Yet
“We were waiting for this one,” said
Gamma-ray bursts are the universe’s most luminous explosions. Astronomers believe most occur when exotic massive stars run out of nuclear fuel. As a star’s core collapses into a black hole, jets of material — powered by processes not yet fully understood — blast outward at nearly the speed of light. The jets bore all the way through the collapsing star and continue into space, where they interact with gas previously shed by the star and generate bright afterglows that fade with time.
This explosion, designated GRB 080916C, occurred at
Nearly 32 hours after the blast,
“Already, this was an exciting burst,” said
With the distance in hand, Fermi team members showed 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 slowest speeds possible for material emitting the prompt gamma rays. Within the jet of this burst, gas bullets must have moved at 99.9999 percent the speed of light. This burst’s tremendous power and speed make it the most extreme recorded to date.
One curious aspect of the burst is a five-second delay separating the highest-energy emissions from the lowest. Such a time lag has been seen clearly in only one earlier burst.
“It may mean that the highest-energy emissions are coming from different parts of the jet or created through a different mechanism,” Michelson said.
The team’s results appear today in the online edition of the journal Science.
NASA’s Fermi Gamma-ray Space Telescope is an astrophysics and particle physics partnership mission, developed in collaboration with the U.S. Department of Energy and important contributions from academic institutions and partners in
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