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

Naked-eye Gamma Ray Burst

A powerful gamma ray burst detected March 19th, 2008 by NASA’s Swift satellite has shattered the record for the most distant object that could be seen with the naked eye.

A powerful gamma ray burst detected March 19th, 2008 by NASA’s Swift satellite has shattered the record for the most distant object that could be seen with the naked eye.Swift’s Burst Alert Telescope picked up the burst at 2:12 a.m. EDT Gamma Ray Burst on March 19, 2008, and pinpointed the coordinates in the constellation Bootes.

Telescopes in space and on the ground quickly moved to observe the afterglow. The burst was named GRB 080319B and registered between 5 and 6 on the visual magnitude scale used by astronomers.the Very Large Telescope in Chile and the Hobby-Eberly Telescope in Texas measured the burst’s redshift at 0.94.

The Mystery of Missing Gamma-ray Bursts

Gamma-ray bursts are by far the brightest and most powerful explosions in the Universe, second only to the Big Bang itself. So it might seem a bit surprising that a group of them has gone missing.

A single gamma-ray burst (GRB) can easily outshine an entire galaxy containing hundreds of billions of stars. Powerful telescopes can see them from clear across the Universe. And because the deeper you look into space, the farther back in time you see, astronomers should be able to see GRBs from the time when the very first stars were forming after the Big Bang.

Farthest GRB
Farthest GRB

Yet they don’t. Gamma-ray bursts from that early epoch seem to be missing, and astronomers are wondering where they are.The answer eventually came from Stan Woosley, a theoretical astrophysicist at the University of California in San Diego. He suggested that when young, supermassive stars with low metal content collapse under their own weight to form black holes, the stars’ rotation funnels the explosive energy into two streamlined jets that shoot out from the stars’ poles, like the axis of a gyro. We only see the burst if one of these two jets happens to be pointed toward Earth. The concentration of energy into narrow jets is why GRBs that we do observe appear so remarkably bright.

The first waves of star formation after the Big Bang should have produced plenty of metal-poor supermassive stars ripe for collapse. If true, GRBs from that epoch should be abundant. So where are they?