A ‘shockingly bright’ gamma-ray burst

May 7, 2013

NASA’s X-Ray Telescope on the Swift satellite took this 0.1-second exposure of GRB 130427A at 3:50 a.m. EDT on April 27, just moments after Swift and Fermi triggered on the outburst. The image is 6.5 arcminutes across. (Credit: NASA/Swift/Stefan Immler)

A record-setting blast of gamma rays from a dying star in a galaxy about 3.6 billion light-years away has wowed astronomers around the world — the highest-energy light ever detected from such an event.

At 3:47 a.m. EDT, April 27, Fermi’s Gamma-ray Burst Monitor (GBM) triggered on an eruption, designated GRB 130427A, of high-energy light in the constellation Leo.

The Fermi Large Area Telescope (LAT) recorded one gamma ray with an energy of at least 94 billion electron volts (GeV), or some 35 billion times the energy of visible light, and about three times greater than the telescope’s previous record.

The GeV emission from the burst lasted for hours, and it remained detectable by the LAT for the better part of a day, setting a new record for the longest gamma-ray emission from a GRB.

The burst subsequently was detected in optical, infrared and radio wavelengths by ground-based observatories.

The maps in this animation show how the sky looks at gamma-ray energies above 100 million electron volts (MeV) with a view centered on the north galactic pole. The first frame shows the sky during a three-hour interval prior to GRB 130427A. The second frame shows a three-hour interval starting 2.5 hours before the burst, and ending 30 minutes into the event. The Fermi team chose this interval to demonstrate how bright the burst was relative to the rest of the gamma-ray sky. This burst was bright enough that Fermi autonomously left its normal surveying mode to give the LAT instrument a better view, so the three-hour exposure following the burst does not cover the whole sky in the usual way. (Credit: NASA/DOE/Fermi LAT Collaboration)

Gamma-ray bursts are the universe’s most luminous explosions. Astronomers think most occur when massive stars run out of nuclear fuel and collapse under their own weight. As the core collapses into a black hole, jets of material shoot 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.

If the GRB is near enough, astronomers usually discover a supernova at the site a week or so after the outburst.

Ground-based observatories are monitoring the location of GRB 130427A and expect to find an underlying supernova by midmonth.


Download additional graphics from NASA Goddard’s Scientific Visualization Studio
Archive of GRB notices from the Gamma-ray Coordination Network
“NASA’s Fermi Telescope Sees Most Extreme Gamma-ray Blast Yet” (02.19.09)
NASA’s Fermi Gamma-ray Space Telescope
NASA’s Swift mission