Scientists say new information has been found regarding an extremely powerful and long-lasting cosmic explosion, leading them to rethink their theories on how stars die.
A research team led by the University of Warwick found examples of the unusual explosions, which create powerful emissions of high energy gamma rays called gamma-ray bursts. While most gamma-ray bursts last less than one minute, these explosions can continue for several hours.
Shawn Bishop, a physicist at the Technical University of Munich in Germany, reported preliminary findings on 14 April at a meeting of the American Physical Society in Denver, Colorado, according to the report published in Nature.
In 2004, scientists reported finding the isotope iron-60, which does not form on Earth, in a piece of sea floor from the Pacific Ocean. They calculated how long ago this radioactive isotope had arrived by using the rate at which it decays over time. The culprit, they concluded, was a supernova in the cosmic neighborhood.
And it was. "It looks like there's something there," Bishop told reporters at the Denver meeting. The levels of iron-60 are minuscule, but the only place they seem to appear is in layers dated to around 2.2 million years ago. This apparent signal of iron-60, Bishop said, could be the remains of magnetite (Fe3O4) chains formed by bacteria on the sea floor as radioactive supernova debris showered on them from the atmosphere, after crossing inter-stellar space at nearly the speed of light.
"I'm really excited about this," says Brian Thomas, an astrophysicist at Washburn University in Topeka, Kansas, who was not involved in the work. "The nice thing is that it's directly tied to a specific event."
