For the first time, scientists have captured vivid images of auroral activity lighting up Neptune’s upper atmosphere using NASA’s James Webb Space Telescope. The data show energetic particles striking Neptune’s ionosphere and releasing a glowing signature.
The discovery confirms what astronomers suspected all along – the evidence was hidden, not absent. Unlike Earth, where auroras dance near the poles, Neptune’s appear in the mid-latitudes due to its unique magnetic field tilt of 47 degrees off its rotation axis. This geometry adds complexity to Neptune’s space weather and helps scientists understand how solar particles interact with distant planetary fields.
The James Webb Space Telescope captured images in June 2023 using its Near-Infrared Spectrograph, revealing the signature glow of a molecule called H3+, which acts as a reliable marker for auroral activity. The observation also showed that Neptune’s upper atmosphere has cooled significantly since 1989, with temperatures now just over half of those in 1989.
The data point to a dynamic upper atmosphere on this giant planet capable of massive temperature shifts, even at a distance of 30 astronomical units from the Sun. Scientists plan to monitor Neptune over a full solar cycle to better understand changes in solar activity and their impact on the planet’s magnetic field and atmospheric shifts.
Source: https://www.earth.com/news/auroras-captured-on-neptune-for-the-first-time-thanks-to-the-webb-telescope