Secret of the origin of cosmic rays is getting trickier


19/04/2012

Huge cosmic explosions known as gamma-ray bursts have been removed from the list of potential sources of the most powerful cosmic rays in the universe. This is the conclusion drawn by researchers in the new study.

Riddle of the strongest origin of cosmic rays has become even more complicated after the circle of suspects have been struck most powerful explosions in the universe.

Some types of cosmic rays differ incredible energy, which can be 100 million times the energy that has been made to scientists in the collider, including the Large Hadron Collider. The sources of these cosmic rays are still unknown.

"There are, in fact, only two theories of the origin of such high-energy first - a stream of particles, driven by the force of gravity of supermassive black holes at the centers of active galaxies. Second - stars collapse into black holes, astronomers observed in the form of gamma-ray bursts," - said one author of the study, Francis HELZ the University of Wisconsin in Madison, in combination supervisor’s largest neutrino observatory IceCube.

Gamma-ray bursts - the most powerful explosions in the universe. Over the period of time from a few milliseconds to a few minutes, they give off the same amount of energy as our sun for all the 10 billion years of its existence.

"It is believed that gamma-ray bursts are either the result of the collapse of supermassive stars - hypernovae or collision of black holes with each other or with neutron stars," - said co-author Spencer Klein. "In both cases, there is a short but powerful emission of radiation."

New data suggest that gamma-ray bursts are not sources of ultrahigh energy cosmic rays.

The researchers used a neutrino detector IceCube.

"This discovery marks the coming of age of neutrino astronomy - the first time we were able to use data on neutrinos to take a fresh look at astrophysical objects and learn something important about them," - said the physicist Nathan Whitehorn.

Astronomers have focused their attention on neutrinos whose energy level suggests a connection with gamma-ray bursts. After analyzing 307 gamma-ray bursts in 2007 and 2009, scientists discovered that their energy level was at least 3.7 times lower than expected. Thus, the color bursts apparently are not the most powerful sources of cosmic rays.

"Our understanding of gamma-ray bursts is still incomplete - with a high level of theoretical uncertainty. I suspect that the community of theorists attempt to push his own interpretation of the results."

The vacant seat for the title of the source of ultrahigh energy cosmic rays, black holes are now occupied in the nuclei of active galaxies.

The efforts of astronomers from the observatory IceCube, in the near future will focus on the study of neutrinos from active galactic nuclei.

The scientists will publish the results in the issue of Nature for April 19.

Original: Csmonitor.com


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