High-energy invaders from space could signal a nearby pulsar, or perhaps dark matter
By Susan Gaidos
February 28th, 2009
Two experiments have detected unusual patterns in cosmic rays pouring into Earth’s atmosphere. One possible source of the unusual rays, which are actually particles, could be a supernova and its cone of ejected material, illustrated here. Other possible sources could be a pulsar or dark matter.M. DeBord, R. Ramaty and B. Kozlovsky/GSFC, R. Lingenfelter/UCSD, NASA
There’s an air of excitement in the astrophysics community, created by a surplus of particles from space invading Earth’s atmosphere.
Balloon flights high in the stratosphere over Antarctica detected electrons in numbers and energies much higher than what usually pours in from space, scientists on a project called ATIC reported in November.
About the same time, a separate report from Milagro, a ground-based detector near Los Alamos, N.M., described two unexpected patches of high-energy protons in the sky. A review of seven years of Milagro data revealed an unusual distribution in the energies of these cosmic rays.
Both experiments seem to show that the Earth is being bombarded with high-energy cosmic rays from a mysterious, nearby source. But scientists aren’t sure whether the results are related.
“You can’t say yes, and you can’t say no, because they’re measuring something different,” says Jordan Goodman, a University of Maryland, College Park, physicist and spokesman for Milagro. The ATIC group “is seeing an excess of electrons, and we’re at higher energies seeing the protons.”
An as yet undetected source, perhaps a pulsar, might generate both protons and electrons at these energies, he says. “If this is the case, this would be very exciting because no one has yet definitively found a source of these high-energy cosmic ray protons.”
But if the events are unrelated, they suggest an even more tantalizing possibility: dark matter.
The findings have inspired efforts to use additional instruments to gather more clues. NASA’s recently launched Fermi Gamma-ray Space Telescope, for instance, could reveal any astrophysical objects that might be candidate culprits.
[b]Not business as usual[/b]
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http://www.sciencenews.org/view/feature/id/40759/title/Cosmic_mystery
