Puzzling pattern of cosmic rays in Antarctica

Last Updated: Saturday, July 31, 2010 - 00:42

Washington: An observatory still under
construction in Antarctica has detected a puzzling pattern in
the cosmic rays bombarding the Earth from space, a discovery
scientists believe could help understand more about how these
rays are formed.

Cosmic rays are highly energetic particles streaming in
from space that are thought to originate in the distant
remnants of dead stars. But it turns out these particles are
not arriving uniformly from all directions.

A "skymap" generated from data collected by the IceCube
Neutrino Observatory at the South Pole, shows that while an
overabundance of cosmic rays coming from one part of the sky,
a lack of such rays coming from another, LiveScience reported.

The advanced telescope, a project by the University of
Wisconsin-Madison, is actually intended to detect other exotic
particles called neutrinos, which are much harder to find.

But, while sifting through their cosmic-ray data to try
to separate it from possible neutrino signals, the researchers
noticed the intriguing pattern of cosmic rays.

"IceCube was not built to look at cosmic rays. Cosmic
rays are considered background," lead researcher Rasha Abbasi
of University of Wisconsin-Madison said in a statement.

"However, we have billions of events of background downward
cosmic rays that ended up being very exciting."

Previous studies have found a similar lopsidedness
(called anisotropy) in the sky over the Northern Hemisphere,
but this was the first time scientists saw that the pattern
extended to the southern sky visible from Antarctica, the
scientists said.

Abbasi said: "At the beginning, we didn`t know what to
expect. To see this anisotropy extending to the Southern
Hemisphere sky is an additional piece of the puzzle around
this enigmatic effect -- whether it`s due to the magnetic
field surrounding us or to the effect of a nearby supernova
remnant, we don`t know." One idea to explain the asymmetry is that a star may have
recently died in a supernova explosion relatively nearby, and
its remnant may be pouring out loads of cosmic rays that would
dominate the signals we receive.

Whether or not the mystery gets solved, scientists said
the observations could help scientists understand more about
how cosmic rays are formed in the first place.

Scientists think that the shells around dead stars, made
of puffed-out layers of gas that were expelled by the star
before it exploded, contain strong magnetic fields that may
act as cosmic particle accelerators, speeding up particles to
close to the speed of light.

"This is exciting because this effect could be the
`smoking gun` for our long-sought understanding of the source
of high-energy cosmic rays," Abbasi said.

IceCube`s findings on cosmic rays are detailed in the
Astrophysical Journal Letters.

PTI



First Published: Saturday, July 31, 2010 - 00:42

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