Original URL: http://www.theregister.co.uk/2008/11/20/cosmic_ray_electrons/

Scientists ponder mysterious source of cosmic rays

Exotic object or dark matter?

By Lester Haines

Posted in Science, 20th November 2008 10:45 GMT

Scientists are pondering the possible source of an "unexpected surplus of cosmic ray electrons at very high energy", and suggest they're either pouring out of an exotic object relatively close to Earth or represent the fall-out from the annihilation of theoretical particles comprising dark matter.

The observation was made by the Advanced Thin Ionization Calorimeter (ATIC) project, led by boffins from Louisiana State University, which soared to 124,000 feet above Antarctica under a helium balloon "about as large as the interior of the New Orleans Superdome".*

The "surplus" electrons - at energies of about 300-800 billion electron volts - "cannot be explained by the standard model of cosmic ray origin", according to ATIC project principal investigator John P. Wefel. He said: "There must be another source relatively near us that is producing these additional particles."

The research team says such a source, either a "pulsar, mini-quasar, supernova remnant or an intermediate mass black hole", would have to lie within 3,000 light years of Earth.

Jim Adams, ATIC research lead at NASA's Marshall Space Flight Center, elaborated: "Cosmic ray electrons lose energy during their journey through the galaxy. These losses increase with the energy of the electrons. At the energies measured by our instrument, these energy losses suppress the flow of particles from distant sources, which helps nearby sources stand out."

The bottom line is, according to Wefel, the possibility of "a very interesting object near our solar system waiting to be studied by other instruments".

Alternatively, for those who like your electron sources a little more esoteric, the cosmic rays could be the result of the destruction of "very exotic particles put forward to explain dark matter". Eun-Suk Seo, ATIC lead at the University of Maryland, proposed: "The annihilation of these exotic particles with each other would produce normal particles such as electrons, positrons, protons and antiprotons that can be observed by scientists."

The results of the ATIC research are published in today's issue of Nature. ®

Bootnote

*Yes, we know - that's not a proper standard and we want the figure in Olympic-sized swimming pools.