for National Geographic News
The most energetic particles in the universe shoot from supermassive black holes at the centers of galaxies, a new study suggests.
Particles known as cosmic rays are constantly bombarding objects in space. The sun bathes Earth in low-energy cosmic rays, astronomers have found, and exploding stars emit medium-energy particles.
But until now researchers had not been able to pinpoint where in the sky the highest-energy cosmic rays are most likely coming from.
These particles can have energies as high as that of a baseball pitcher's fast-ball—but all that energy is packed inside a lone proton a hundred million times smaller, the study authors say.
The new research is based on data from the Pierre Auger Observatory on the plains of Argentina, which was used to search for signs of high-energy cosmic rays.
"When you look at the highest-energy cosmic rays from the most violent sources, they point back to their sources," said study co-author Paul Mantsch of Fermilab in Batavia, Illinois.
The researchers found that the high-energy rays seem to be coming from areas of the sky known to contain huge, belching black holes called active galactic nuclei.
The study is cautious about its implications, stating that the results "cannot be used alone as proof that [active galactic nuclei] are the sources."
But some members of the study team believe they now have the best possible answer.
"We discovered the sources of the highest-energy particles in the universe," said team member Miguel Mostafa of the University of Utah in Salt Lake City.
Now that we found the sources," he added, "we are one step closer to knowing what physical process can accelerate particles to these ultrahigh energies."
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