Huge Cosmic Explosions Fueled by Magnetism

The death of one star can sometimes outshine a galaxy of billions of stars. That's because when some very massive stars end their lives in supernova explosions, they release a surge of light known as a gamma ray burst.

Now scientists have found evidence that magnetic fields are behind these rare events. Theorists have predicted that magnetic fields could explain how gamma ray bursts (GRBs) produce jets of bright radiation that shoot out into the universe. But no one has observed the presence of a magnetic field in a gamma ray burst until now.

On Jan. 2, 2009, a gamma ray burst erupted and was quickly detected by NASA?s Swift satellite, which makes continuous scans of the cosmos in hopes of catching one of these outbursts, as they generally last only seconds. Swift reported the burst immediately to telescopes around the world, and the robotic Liverpool Telescope on the Canary Island of La Palma automatically began observing it.

The telescope was fitted with a filter that detects polarized light, or light that is electrically and magnetically aligned in a certain direction. Indeed, the observatory found polarized light in the gamma ray burst signature, which told the researchers that the light originated in a magnetic field.

"This breakthrough observation gives us the first measurement of magnetic fields in the afterglow of a GRB," said Swift lead scientist Neil Gehrels of NASA?s Goddard Space Flight Center in Greenbelt, Md.

The researchers ? led by astronomer Iain Steele, director of the Liverpool Telescope and a professor at Liverpool John Moores University in England ? published their findings in the Dec. 10 issue of the journal Nature.

"This is a first indication that magnetic fields are very important [in GRBs]," Steele told SPACE.com. "I think this is a good step forward to understanding the energetics in the jet and the role of magnetic fields."

Gamma ray bursts only occur in a small subset of supernovas, and astronomers think they might be associated with the deaths of more massive stars. The researchers hope to observe more GRBs in the future for confirmation of the presence of magnetic fields, and to learn more about what powers these luminous eruptions.

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