Mysterious Source of High-Energy Cosmic Radiation Discovered
November 19, 2008
ATIC high-energy electron counts. The triangular curve fitted to the data comes from a model of dark-matter annihilation featuring a Kaluza-Klein particle of mass near 620 GeV. Details may be found in the Nov. 20, 2008, edition of Nature: "An excess of cosmic ray electrons at energies of 300-800 Gev," by J. Chang et al.
(PhysOrg.com) -- Scientists announced Wednesday the discovery of a previously unidentified nearby source of high-energy cosmic rays. The finding was made with a NASA-funded balloon-borne instrument high over Antarctica.
Researchers from the Advanced Thin Ionization Calorimeter (ATIC) collaboration, led by scientists at Louisiana State University, Baton Rouge, published the results in the Nov. 20 issue of the journal Nature. The new results show an unexpected surplus of cosmic ray electrons at very high energy -- 300-800 billion electron volts -- that must come from a previously unidentified source or from the annihilation of very exotic theoretical particles used to explain dark matter.
"This electron excess cannot be explained by the standard model of cosmic ray origin," said John P. Wefel, ATIC project principal investigator and a professor at Louisiana State. "There must be another source relatively near us that is producing these additional particles."
According to the research, this source would need to be within about 3,000 light years of the sun. It could be an exotic object such as a pulsar, mini-quasar, supernova remnant or an intermediate mass black hole.
"Cosmic ray electrons lose energy during their journey through the galaxy," said Jim Adams, ATIC research lead at NASA's Marshall Space Flight Center in Huntsville, Ala. "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 scientists point out, however, that there are few such objects close to our solar system.
"These results may be the first indication of a very interesting object near our solar system waiting to be studied by other instruments," Wefel said.
An alternative explanation is that the surplus of high energy electrons might result from the annihilation of very exotic particles put forward to explain dark matter. In recent decades, scientists have learned that the kind of material making up the universe around us only accounts for about five percent of its mass composition. Close to 70 percent of the universe is composed of dark energy (so called because its nature is unknown). The remaining 25 percent of the mass acts gravitationally just like regular matter, but does little else, so it is normally not visible.
The nature of dark matter is not understood, but several theories that describe how gravity works at very small, quantum distances predict exotic particles that could be good dark matter candidates.
"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," said Eun-Suk Seo, ATIC lead at the University of Maryland, College Park.
The 4,300-pound ATIC experiment was designed to be carried to an altitude of about 124,000 feet above Antarctica using a helium-filled balloon about as large as the interior of the New Orleans Superdome. The goal was to study cosmic rays that otherwise would be absorbed into the atmosphere.
For information on NASA's scientific balloon program, visit: http://sites.wff.nasa.gov/code820/
Provided by NASA
Dec 18, 2009 |
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2 hours ago
So what, precisely, was discovered?
The article poses questions and possible causes of observations. What was the discovery?
Yes, but scientists seem to be desparate to find evidence of dark matter. Everything must be twisted to support the dark matter kludge.
Unless gravity acts differently over great distances. Perhaps gravity-wells the size of galaxies behave differently.
Alternatively, I've never been entirely convinced that the missing mass is non-baryonic. Maybe it IS normal matter that just isn't visible for some reason.
The point being that when current theories don't explain observations, scientists try to find a theory that does. I've never been able to understand the attitude of people who think that this is somehow nefarious. Would you rather that they just kept insisting on newtonian physics regardless of observations?
zeev
You mean something like there is not enough light in the space between stars and such to reflect on the dust in space?
Thanks!
Zac
And I cannot but laugh when I read the last part-I mean, "there are theories which predict...". There are theories which consider Man was created 5000 years ago! If you ask me, until the moment we see a proof quantum gravity works, it's simply not worth mentioning. "Sounds nice" is not like explain nicely.
And there are actually much more simple theories that could solve many problems, on "general relativity" level. But let's see what will come out of them.
http://tothefutur...post.com