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Scientists link birth of cosmic rays to shock waves of exploding stars

SHARE Scientists link birth of cosmic rays to shock waves of exploding stars

Cosmic rays, mysterious high-energy particles that constantly zip through planets and even people, are born in the shock waves of exploding stars and sent racing outward at near the speed of light, according to a new theory.

Physicists say the theory solves a puzzle of how cosmic rays can make some heavy elements, including boron, a chemical used in ordinary household soap."If you've ever used borax, you have washed your hands in old broken up cosmic rays," Richard Lingenfelter of the University of California, San Diego, said Thursday. "The boron comes from cosmic ray interactions."

The new theory by Lingenfelter, Reuven Ramaty of the Goddard Space Flight Center in Maryland and Benzion Kozlovsky of Tel Aviv University in Israel was presented at the national meeting of the American Astronomical Society.

Cosmic rays have puzzled astrophysicists for almost a century. It was known they bathed the universe, speeding with no apparent harm through planets, objects, people.

"A dozen pass through this piece of paper every second," Lin-gen-felter said at a news conference. "More than 10 billion go through your body in a lifetime."

The rays are nuclei of atoms, and their passage is not noticeable, although some studies have suggested that cosmic rays may break chromosomes and cause mutations. It has been suggested that such mutations over millions of years could be a factor in biological evolution.

When primary cosmic rays collide with atoms of the atmosphere, they create what is called "secondary cosmic rays." Only the most energetic of these reach the ground.

Primary cosmic rays have been detected using balloons and spacecraft. The rays leave marks in detectors made of plastic layers.

The path of cosmic rays is twisted by magnetic fields in the galaxy, making it impossible to pinpoint their origin.

In 1990, it was determined the high-speed particles originate from within the Milky Way galaxy, but their exact source was unknown. Experts suggested cosmic rays were created in supernova explosions, but the precise mechanism of how the particles could be accelerated at such high rates of speed was unknown.

When a supernova occurs, ionized gas is shot out into space at thousands of miles per second. It creates a powerful shock wave that moves outward at high speeds for thousands of years.

In the new theory, Lingenfelter and his colleagues suggest that this shock wave is the key to cosmic rays.

Lingenfelter said he believes heavy elements made by the star and sent speeding outward by its explosion condense into dust grains of graphite and metal oxides. These are shot into the cosmos "like tiny bullets," he said, and are part of an expanding high speed cloud of superheated ionized gas called plasma.

The gas slows, but the grains race through the plasma. Atoms are ripped from the grains and become electrically charged. These are then accelerated to near the speed of light by the shock wave, becoming the cosmic rays, the theory states.