James Webb Space Telescope Captures Neptune’s Auroras for the First Time

NASA’s James Webb Space Telescope has captured stunning images of auroral activity on Neptune, the distant ice giant. Yes, this is the same phenomenon that you see right here on Earth, as they typically occur when energetic particles get trapped in a planet’s magnetic field and collide with gases in the upper atmosphere, releasing energy in the form of light.

Webb made these observations were made in June 2023 using its Near-Infrared Spectrograph (NIRSpec), and show Neptune’s auroras as bright cyan spots. Unlike Earth, they appear at mid-latitudes on the ice giant rather than near the poles.

Astronomers had seen hints of auroral activity on Neptune during Voyager 2’s 1989 flyby, but confirming and imaging them clearly had been a challenge. Webb’s sensitivity to infrared light finally made it possible, detecting a strong emission line from the trihydrogen cation, a molecule known to glow during auroral events.

Turns out, actually imaging the auroral activity on Neptune was only possible with Webb’s near-infrared sensitivity. It was so stunning to not just see the auroras, but the detail and clarity of the signature really shocked me,” said Henrik Melin, lead author from Northumbria University, who conducted the research while at the University of Leicester.