Thursday, 3 May 2012

Cosmic rays leave scientists in the dark

One of the paper's authors, Associate Professor Jenny Adams from New Zealand's University of Canterbury, says tracing cosmic rays back to their source is impossible because they're deflected by magnetic fields and galaxies Various models predict gamma ray bursts are the only events capable of producing enough energy to accelerate cosmic rays. Cosmic rays are highly energetic charged particles such as protons and heavier atomic nuclei, that strike the Earth from deep space with 100,000,000 times more energy than can be created in particle accelerators like CERN's Large Hadron Collider. A report in the journal Nature by scientists from the IceCube collaboration, concluded there wasn't enough evidence to link gamma ray bursts and cosmic rays. Researchers searching for the source of cosmic rays are going back the drawing board after ruling out gamma ray bursts as the most likely source.

Because they're neutral they'll point back to their source. "The problem is, we found no neutrinos coming from gamma ray bursts," says Adams. "

"That's why the IceCube neutrino detector was built. "And if there aren't neutrinos, there can't be cosmic rays. I guess in some ways it's disappointing. "

"We built IceCube to detect Gamma Ray Burst neutrinos, we didn't expect not to find any. "The solution was finding extremely weakly interacting subatomic particles called neutrinos which aren't effected by magnetic fields," says Adams. "
Underground detector

Buried up to two kilometres under the Antarctic ice at the South Pole, IceCube is the only instrument big enough to detect neutrinos generated by gamma ray bursts. "Wherever cosmic rays are produced, neutrinos should also be produced. "

"But it's also deepened the mystery, because we now have to look for new possible sources to solve the riddle. "

"The Ice Cube data we published in Nature came when the detector was only between half and three quarters complete," says Adams. Now with Ice Cube finished and up to full capacity, Adams believes the search can focus on active galactic nuclei. They were a good candidate. But one of the papers other authors, Dr Gary Hill from the University of Adelaide, isn't so confident. "Gamma ray bursts were our big shot. " Adams says active galactic nuclei such as quasars and blazars, powerful energy beams produced by supermassive black holes, may be possible candidates. "Hopefully we'll find neutrinos or rule out some more models as to where cosmic rays can be produced," says Adams. "The statistical significance between cosmic rays and active galactic nuclei hasn't grown over time despite more observations," says Hill. "

"It really is a mystery because we can't figure out where cosmic rays could come from.

1 comment:

  1. Sorry, I thought that the solar wind that drags out behind Earth in the tail became so thinned it snapped and flipped back suddenly bringing up to light-speed all those cosmic rays?