Brown dwarf stars host powerful aurora displays just like planets, astronomers have discovered.
The so-called failed stars, which are difficult to detect and also remain hard to classify, are too massive to be planets but physicists from the Universities of Sheffield and Oxford have revealed that they host powerful auroras just like Earth.
The international team of researchers made the discovery by observing a brown dwarf 20 light years away using both radio and optical telescopes. Their findings provide further evidence that suggests these stars act more like supersized planets.
Dr Stuart Littlefair, from the University of Sheffield's Department of Physics and Astronomy, said: "Brown dwarfs span the gap between stars and planets and these results are yet more evidence that we need to think of brown dwarfs as beefed-up planets, rather than "failed stars".
"We already know that brown dwarfs have cloudy atmospheres - like planets - although the clouds in brown dwarfs are made of minerals that form rocks on Earth now we know brown dwarfs host powerful auroras too."
He added: "Sometimes the best thing about a scientific result is simply the thrill of discovering something exciting and cool. The northern lights on Earth are one of the most spectacular and beautiful things you can see.
"I've always wanted to see them, but have never got the chance. It's particularly ironic that I got to discover an auroral light show which is vastly more powerful and many light years away!"
Auroral displays result when charged particles manage to enter a planet's magnetic field. Once within the magnetosphere, those particles get accelerated along the planet's magnetic field lines to the planet's poles where they collide with gas atoms in the atmosphere, producing the bright emissions associated with auroras.
During the study the international research team, led by Professor Gregg Hallinan from the California Institute of Technology, conducted an extensive observation campaign of a brown dwarf called LSRJ1835+3259.
The team used the most powerful radio telescope in the world, the National Radio Astronomy Observatory's Karl G. Jansky Very Large Array (JVLA) in New Mexico, as well as optical telescopes including Palomar's Hale Telescope and the W.M Keck Observatory's telescopes to make their ground breaking observations.
Using the JVLA they detected a bright pulse of radio waves that appeared as the brown dwarf rotated around. The object rotates every 2.84 hours, so the team were able to watch nearly three full rotations over the course of a single night.