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Powerful aurora spotted on distant brown dwarf

Like Earth, the brown dwarf possesses an active electromagnetic field and outer atmosphere.

By Brooks Hays
A faraway brown dwarf has been found to host polar auroras. Photo by Chuck Carter and Gregg Hallinan/Caltech
A faraway brown dwarf has been found to host polar auroras. Photo by Chuck Carter and Gregg Hallinan/Caltech

PASADENA, Calif., July 30 (UPI) -- Scientists have spotted an aurora much more elusive than the Earth-bound Northern Lights -- an electromagnetic light show at the poles of a brown dwarf 18 light-years away.

The brown dwarf, which is an object somewhere between a gas giant and a small star, is called LSRJ1835+3259 and found in the Lyra constellation. Brown dwarfs are failed stars -- stars that didn't quite have the heft to sustain stellar fusion. In behavior, it's more similar to the Earth than it is to our sun.

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While studying the failed star using a powerful radio telescope, a team of international researchers noticed changes in the light streaming off the dwarf's poles. The light was an example of an alien aurora -- one a million times brighter than the Northern Lights, and 10,000 times more powerful than auroras witnessed on gas giants in our own solar system.

Researchers reported their findings this week in the journal Nature, describing a faraway aurora that was more red than green. Auroras of any kind are the result of high-energy particles colliding with gas in the atmosphere.

Like Earth, the brown dwarf possesses an active electromagnetic field and outer atmosphere.

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"All the magnetic activity we see on this object can be explained by powerful auroras," Gregg Hallinan, a researcher with the California Institute of Technology (Caltech), said in a news release. "This indicates that auroral activity replaces solar-like coronal activity on brown dwarfs and smaller objects."

The discovery is likely to reinvigorate the debate over whether brown dwarfs should be classified as stars or planets. Scientists have long disagreed over the dividing line.

"In science, new knowledge often challenges our understanding," said Garret Cotter, a researcher at the University of Oxford. "We know how controversial the situation was with Pluto, where astronomers had to look hard to try to decide if it is fundamentally one of the major planets of the solar system, or the first of the Kuiper Belt objects."

"Now, up at the other end of the size scale," said Cotter, "we are challenged by seeing objects that traditionally would have been classified as stars, but seem to be showing more and more properties that make them look like super-sized planets."

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