Gamma ray burst polarization studied

LIVERPOOL, England, March 19 (UPI) -- A British-led international team of astronomers has recorded the earliest measurement of the optical polarization of a gamma ray burst.

The British, Italian, French and Slovenian scientists, using the world's largest robotic astronomical telescope, recorded the measurement 203 seconds after the start of the cosmic explosion.

Gamma ray bursts are the most instantaneously powerful explosions in the universe and are identified as brief, intense and completely unpredictable flashes of high energy gamma rays.

The measurement was obtained nearly 100 times faster than any previously published optical polarization measurement for a gamma ray burst afterglow and answers some fundamental questions about the presence of magnetic fields.

Team leader Carole Mundell of Liverpool John Moores University said: "Our new measurements, made shortly after the gamma ray burst, show that the level of polarization in the afterglow is very low. Combined with our knowledge of how the light from this explosion faded, this rules-out the presence of strong magnetic fields in the emitting material flowing out from the explosion -- a key element of some theories of GRBs."

The finding, which is said to provide new insight into gamma ray burst physics, appears in the journal Science.