Auroras are usually seen from Earth as northern and southern lights. However, now, astronomers have witnessed a similar event taking place outside the solar system for the first time ever.
Brown dwarfs are often thought of as failed stars — vast accumulations of mostly hydrogen and helium gas that never accumulated enough matter to ignite thermonuclear reactions at their core. Although more massive than even mighty Jupiter, they are challenging to detect, as they give off little heat and no light of their own.
Astronomers utilized both optical and radio telescopes to study LSR J1835+3259, a brown dwarf located roughly 20 light years from our own sun. They discovered, that just like planets, including Earth and Mars in our own solar system, brown dwarf stars exhibit auroras.
"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. Sometimes the best thing about a scientific result is simply the thrill of discovering something exciting and cool," said Stuart Littlefair from the University of Sheffield.
Auroras are seen on Earth when charged particles encounter the magnetic field of our planet. They are then accelerated until they strike molecules in the atmosphere. This results in the release of electromagnetic radiation, seen as the often-dazzling northern and southern lights. On LSR J1835+3259, a mysterious dynamo effect drives the process, researchers report.
Astronomers taking part in the study utilized some of the most powerful astronomical instruments on the surface of the Earth to make their observations. Data was collected from the Keck observatory in Hawaii, the Hale Telescope on Mount Palomar and the largest radio telescope network in the world, the Very Large Array (VLA), located in New Mexico. Variations in radio emissions were compared with optical patterns and found to be identical. This suggested a bright object on the body, seen as the brown dwarf rotated once every two hours and 50 minutes.
"What we see on this object appears to be the same phenomenon we've seen on Jupiter, for example, but thousands of times more powerful. This suggests that it may be possible to detect this type of activity from extrasolar planets, many of which are significantly more massive than Jupiter," Gregg Hallinan from the California Institute of Technology (Caltech) said.
This new study could lead astronomers away from thinking of brown dwarfs as failed stars and more toward modeling the bodies as overgrown Jupiters rather than poor imitations of a sun.
Ironically, Littlefair, the person largely credited with the discovery of the first aurora seen outside the Solar System, has never seen the displays live here on Earth.