NASA Studies Aurorae on Brown Dwarf

Artist concept portrays the brown dwarf W1935, which is located 47 light-years from Earth | Image by NASA

NASA scientists are studying potential signs of aurorae on a distant brown dwarf using the James Webb Space Telescope.

The scientists have documented evidence of the phenomenon on a distant brown dwarf known as W1935, discovering infrared emissions from methane gas. This celestial body, located about 47 light-years from Earth, is the first and coldest auroral candidate outside the solar system with a methane emission signature, according to NASA.

A brown dwarf is a celestial body that is smaller than a star but is 10 to 80 times more massive than gas giants such as Jupiter. These objects may also be called “failed stars” because they do not have enough mass to start fusion reactions, according to CalTech.

“On Earth, aurorae are created when energetic particles blown into space from the Sun are captured by Earth’s magnetic field. They cascade down into our atmosphere along magnetic field lines near Earth’s poles, colliding with gas molecules and creating eerie, dancing curtains of light,” explains a press release.

“For isolated brown dwarfs like W1935, the absence of a stellar wind to contribute to the auroral process and explain the extra energy in the upper atmosphere required for the methane emission is a mystery.”

“We expected to see methane because methane is all over these brown dwarfs. But instead of absorbing light, we saw just the opposite: The methane was glowing,” said Jackie Faherty, leader of the team studying W1935. “My first thought was, what the heck? Why is methane emission coming out of this object?”

Scientists used telescopic data and computer models to study W1935 and other brown dwarfs like it. Unlike the other celestial bodies, whose temperature was cooler with increasing altitude, this brown dwarf showed signs that temperature was increasing with altitude.

“This temperature inversion is really puzzling,” said Ben Burningham, a co-author of the study. “We have seen this kind of phenomenon in planets with a nearby star that can heat the stratosphere, but seeing it in an object with no obvious external heat source is wild.”

Scientists took note of similar temperature inversions in our own solar system with the gas giants Jupiter and Saturn. They aim to use data from our own solar system and that of the brown dwarf to inform our understanding of aurorae.

“With W1935, we now have a spectacular extension of a solar system phenomenon without any stellar irradiation to help in the explanation,” said Faherty. “With Webb, we can really ‘open the hood’ on the chemistry and unpack how similar or different the auroral process may be beyond our solar system.”

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