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Black holes blamed for super-charged cosmic rays

That's 'active galactic nuclei' to you, sonny

You've always suspected it*, and now some properly clever boffins think they've found the data to prove it. Yes, a rare breed of supermassive black hole, otherwise known as active galactic nuclei, are the most likely source of the super-charged cosmic rays that batter our tiny planet from time to time.

The particles zip through space at just a shave away from the speed of light, carrying astonishing amounts of energy, roughly 100 million times that of the most energetic particle ever created in an accelerator on Earth. The challenge facing scientists was to find a way that a particle could become imbued with such huge energies.

They don't hit us very often, relative to their less energetic cousins, with roughly one particle per square kilometre, per century hitting the planet, Scientific American reports.

Reports of the research variously have the rays striking our upper atmosphere with the force of a fast pitch baseball (whatever that might be...), the energy of a nicely hit tennis ball, or the punch of a rifle shot. (That's all very well, but what is it in Norrises, right?)

A group called the Pierre Auger Collaboration, composed of almost 400 scientists from 17 countries, says it has now found evidence that points the finger at the supermassive black holes that lie at the centre of some galaxies.

The researchers used a network of 1,400 particle detectors spread over an area of 1,200 square miles (0.144 times the size of Wales, in Register standard units), along with 24 ground based telescopes scattered across western Argentina.

The size of the observation grid has allowed the team to catch plenty of the rare rays in the act, and track them back to their sources. Of the millions of rays that flew into our planet since the grid went online in 2004, 77 qualified as super-charged. Of these, the 27 most energetic were traced back to areas of the sky with active galactic nuclei.

James Cronin, a Nobel-prize winning physicist at the University of Chicago and the co-founder of the Auger observatory told the New York Times: "The age of cosmic-ray astronomy has arrived. We're only just getting started."

The work is published in the current issue of Science. ®

*What do you mean, you never gave it a moment's thought?

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