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Space + FlightSpace & Flight

Vivid Extrasolar Aurora Solves Astronomical Mystery

ByAbbey InterranteNOVA NextNOVA Next

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The auroras that grace the skies above Earth are known for their ethereal beauty and spectacular colors. But they’re nothing compared with what scientists recently found on a brown dwarf 18 light years away— an aurora one million times brighter than the northern lights.

Brown dwarfs have baffled astronomers because they routinely light up then fade with no explanation. They aren’t massive enough to generate the internal heat necessary to be called stars, but they’re still brighter than planets.

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When scientists studied brown dwarf LSR J1835+3259, they noticed that it flashed once every two hours as it rotated. They decided to take a closer look with the Hale telescope in San Diego and the National Radio Astronomy Observatory in New Mexico, which captured optical and radio signals from the substellar object. Such signals are also emitted from commonly known auroras, though they had never been observed outside our solar system.

Star
Hydrogen causes the aurora to emit a color too red for the human eye to see.

Ian Sample, of The Guardian, explains further:

On Earth, the northern lights are driven by electrons that stream out of the sun into the planet’s magnetic field, which drives them towards the magnetic north pole where they slam into atoms in the atmosphere. Similar displays are seen on other planets, and are particularly intense on Jupiter, where auroras driven by gases coming from its moon, Io, gleams with ultraviolet light.

The newly discovered aurora lies in the constellation Lyra, just 18 light years from Earth. When electrons in the brown dwarf’s atmosphere collide with oxygen and sodium, they spark a shower of green and yellow light, and when they hit hydrogen, they emit a burst of infrared.

Some scientists are arguing that brown dwarfs, which are often called “failed stars,” should be considered giant planets. Scientists showed that some have auroras and atmospheres—just like the planets in this solar system.

J1835 is 80 times more massive than Jupiter but is about the same size. Even with the shockingly bright aurora, it’s 150,000 times too dim to be seen with the naked eye. However, it’s still bright enough to be captured in great detail by some telescopes, giving astronomers a new way to search for brown dwarfs.

Illustration Credit: Chuck Carter and Gregg Hallinan/Caltech