Webb spots Neptune's hidden auroras amid its tilted magnetosphere
NASA’s James Webb Space Telescope detected the H3+ auroral fingerprint in Neptune’s upper atmosphere, providing the first direct evidence of auroras on the ice giant and a map of their locations. The auroral ovals sit well away from Neptune’s rotational poles because the planet’s magnetic field is tilted about 47 degrees and offset from the center, explaining why Voyager 2 saw faint, misplaced hints in 1989. Webb’s observations also show the upper atmosphere was several hundred degrees cooler than Voyager’s measurements, helping to explain why H3+ signals had been hard to detect before. The findings reinforce Neptune’s oddly tilted magnetosphere, while leaving room for future measurements to build a temperature record and track auroral changes; there is no funded mission to return to Neptune yet.
