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Should We Worry About A Gamma Ray Blast?

January 24, 2013
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An intense, two-second burst of gamma rays apparently hit the earth in the eighth century. Nobody noticed. Had it occurred today, it would have devastated much of the infrastructure of civilization worldwide.

But don’t worry: It won’t happen again. Probably.

Scientists only recently learned about the big radiation burst. Just last year, Fusa Miyake, a cosmic-ray physicist from Nagoya University in Japan, and colleagues revealed evidence of the event. In a study published in Nature, they described high levels of carbon-14 and beryllium-10 in tree rings formed in 775, suggesting that a big blast of radiation struck the Earth in 774 or 775.

Astronomers Valeri Hambaryan, PhD, and Ralph Neuhäuser, PhD, of the Astrophysical Institute of the Friedrich Schiller University of Jena in Germany, think they know the source. After ruling out everything from a solar flare to a supernova, they conclude that two compact remnants of collapsed stars—black holes, neutron stars, or white dwarfs—collided and merged. Such an event would release immense bursts of gamma radiation. But it would not produce visible light, which would account for the lack of any notable observed celestial phenomena at the time.

Drs. Hambaryan and Neuhäuser lay out their theory in an article published online this week in Monthly Notices of the Royal Astronomical Society. They think the colossal collision occurred 3,000 to 12,000 light years away. In a Royal Astronomical Society news release, Dr. Neuhäuser warned:

If the gamma ray burst had been much closer to the Earth, it would have caused significant harm to the biosphere. But even thousands of light years away, a similar event today could cause havoc with the sensitive electronic systems that advanced societies have come to depend on.

Astronomer Phil Plait, PhD, in his Bad Astronomy blog, says reassuringly, “We expect to see one of these events in our galaxy about once per million years or so.”

He adds, not so reassuringly, that if such an event did occur today:

Our atmosphere would absorb all the radiation, and we’d be safe enough from all that here on Earth’s surface, but we’d lose satellites, the interaction of the high-energy gamma rays would blow out power grids all over the planet, and our civilization would be in big trouble.

Yikes. Let’s just focus on the “once per million years” part.

Related seminar: Radiology Review


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