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Scientists Surprised by X-rays from Lab Lightning

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Sparks created in a lab give off X-rays, scientists announced Monday.

X-rays are a byproduct of high-energy electron discharges in the Sun, in exploding stars, and even in lightning. Many scientists did not expect sparks alone to do the trick.

Researchers at Florida Institute of Technology brought their equipment, which had detected X-rays in lightning, into the lab. Half the team expected to see X-rays and the other half did not.

In sparks of 1.5 million to 2 million volts, the researchers indeed recorded X-rays that were remarkably similar to those produced by lightning.

"This amazed us. It opens the door to answering really big questions about lightning by generating it in the lab," said team member Hamid Rassoul. "It also tells us that we have a lot to learn about how even small sparks work."

X-rays are a form of electromagnetic radiation, on a spectrum that runs from radio waves on the low end to gamma rays on the high end and includes visible light, too.

Scientists don't know why lightning spawns X-rays. They theorize it involves a "runaway breakdown" of the air, in which electrons escape their normal bonds and gain very large energies.

"We didn't think [X-rays] could be made so easily in the air," said study leader Joseph Dwyer. "The results should allow for the detailed laboratory study of runaway breakdown, a mechanism that may play a role in thunderstorm electrification, lightning initiation and propagation, and terrestrial gamma-ray flashes."

The discovery is published in the journal Geophysical Research Letters.

Robert Roy Britt
Rob was a writer and editor at Space.com starting in 1999. He served as managing editor of Live Science at its launch in 2004. He is now Chief Content Officer overseeing media properties for the sites’ parent company, Purch. Prior to joining the company, Rob was an editor at The Star-Ledger in New Jersey, and in 1998 he was founder and editor of the science news website ExploreZone. He has a journalism degree from Humboldt State University in California.