An Engine for Mind-Boggling Blasts

Astrophysicist Pawan Kumar of the University of Texas in Austin and colleagues argue that the jets giving rise to GRBs are not made of matter but actually are powerful magnetic fields transporting energy away from the collapsing stars. The researchers analyzed data from 10 GRBs collected by NASA's Swift satellite and found that the sources of the bursts were located about 10 billion kilometers from the sites of the stellar collapses--about 100 times farther than expected. By the time jets of ordinary matter would have reached that distance, they could not have retained enough energy to generate gamma rays.