Cosmic rays believed to start in black holes

By Julie Steenhuysen

CHICAGO (Reuters) - Ultra-high energy cosmic rays -- particles that pack the punch of a rifle shot -- make their way to Earth from massive black holes in nearby galaxies, scientists said on Thursday, in a finding that may solve a mystery that has puzzled physicists for decades.

This sub-atomic matter, they believe, likely breaks free just before stars, gas and dust are gobbled up by the gravitational pull of black holes so dense that not even light can escape.

The finding, published in the journal Science, begins to explain how a single particle carrying so much energy could make its way to Earth.

"These cosmic rays have puzzled people for years," said Alexander Kusenko, a professor of physics and astronomy at the University of California, Los Angeles, who worked on the study with physicists and astronomers from 17 countries.

"This is a fundamental discovery," said Nobel physics laureate James Cronin of the University of Chicago. "The age of cosmic-ray astronomy has arrived."

Scientists have long suspected that ultra-high energy cosmic rays come from outside our galaxy, but researchers now believe they travel as far as 250 million light-years to Earth. A light year is the distance light travels in one year, or about 5.8 trillion miles.

"This particle has enormous energy. It carries as much energy as the punch of a boxer," Kusenko said in a telephone interview.

"A single particle carries as much energy as a bullet from a rifle," added Katsushi Arisaka, a UCLA professor of physics.