© Caltech/Chuck Carter
Melodie Kao (Arizona State University) and colleagues used the National Science Foundation's Karl G. Jansky Very Large Array to detect high-frequency radio emissions from four nearby brown dwarfs, with masses between 12 and 30 times the mass of Jupiter. Their magnetic fields are hundreds to thousands of times stronger than those around the Sun and power brilliant, radio-emitting aurorae similar to the Northern Lights on Earth. The results appear in the Astrophysical Journal Supplement Series (free preprint).
Among the brown dwarfs under study is SIMP0136, an object with a mass just below 13 times the mass of Jupiter - just below the dividing line that separates planets from brown dwarfs. Floating in interstellar space 20 light-years away, this planet is isolated - a "rogue planet."
On Earth, brilliant aurorae appear around the North and South Poles, where charged particles from the Sun stream in along Earth's magnetic field and crash into the upper atmosphere. A similar mechanism works at Jupiter, where the particles come from Jupiter's moons rather than the Sun. But unlike Earth and Jupiter, SIMP0136 is on its own - it either formed by itself or was flung out of another solar system. Either way, it doesn't have a parent star, so its aurorae can't come from interactions with a stellar wind.
Perhaps the planet hosts a moon of its own - but it's too soon to come to that conclusion. More observations are needed to confirm the origin of the radio emissions.
Comment: Some say 'Space is the final frontier' but perhaps the real final frontier is 'cooperation and co-existence'!