‘ALIEN AURORA’ MAY HAVE BEEN SPOTTED ON NEARBY FAILED STAR

This brown dwarf doesn’t shine with fusion light, but may have found a way to put on a dazzling display of its own

Brown dwarfs, which are often referred to as ‘failed stars’, are a funny sort of celestial body. They’re too large to be classified as a planet, but too small to start the fusion processes required to be a fully fledged star.

One such brown dwarf is named CWISEP J193518.59–154620.3 (or W1935 to its friends) and astronomers think they may have uncovered evidence for aurorae on it (illustrated below). The aurorae are similar to the Northern Lights we observe towards the north and south poles on Earth, although thousands of times brighter.

The study, which was published in the journal Nature, used NASA’s James Webb Space Telescope (JWST) to observe W1935, which is about 47 light-years from Earth. When the tennis court- sized space telescope was pointed in the direction of the brown dwarf, the team noticed an unusual glow.

“We expected to see methane because methane is all over these brown dwarfs. But instead of it absorbing light, we saw just the opposite – the methane was glowing,” said Dr Jackie Faherty, lead author of the study. . “My first thought was, ‘ What t the heck? Why is methane e emission coming out of f this object?’”

Computer modelling of W1935, which the team used to explain the strange methane emission, provided another surprise: the brown dwarf likely has a temperature inversion, where the atmosphere becomes warmer with increasing altitude. This phenomenon is common in planets orbiting stars, but is unexpected for an isolated object like W1935, which lacks an apparent external heat source. To unravel this mystery, the researchers turned to Jupiter and Saturn, which also exhibit methane emission and temperature inversions. The cause of these features on our Solar System giants is aurorae – spectacular light displays resulting from high-energy particles interacting with the planet’s magnetic fields and atmospheres. Aurorae are known to heat the upper atmospheres of planets, which would fit nicely with the team’s observations.

And yet, one final piece of the puzzle was missing. High- energy auroracausing particles in our Solar System come from the Sun, blown out as solar wind into space. But W1935 lacks a host star (making it ‘ rogue’) and so ruling out solar wind as a possible explanation. The researchers think a yet-to-be-discovered moon might be responsible for the observed aurora on W1935 – just as moons around Jupiter and Saturn enhance their aurorae.