For the first time, NASA’s James Webb Space Telescope has captured bright auroral activity on Neptune. This detection was made possible by the telescope’s near-infrared sensitivity, allowing astronomers to see details and clarity in the auroras that were previously invisible.
Auroras occur when energetic particles from the Sun become trapped in a planet’s magnetic field and strike the upper atmosphere, releasing energy and creating the signature glow. Astronomers had seen hints of auroral activity on Neptune before, but imaging and confirming it had evaded them until now.
The data was obtained in June 2023 using Webb’s Near-Infrared Spectrograph. In addition to the image of the planet, astronomers also found an extremely prominent emission line signifying the presence of trihydrogen cation (H3+), a clear indicator of auroral activity. The glowing aurora appears as splotches represented in cyan.
Neptune’s auroras are different from what is seen on Earth or other planets. They are located at mid-latitudes, not just near the poles, due to Neptune’s unique magnetic field tilted by 47 degrees from its rotation axis. This tilt causes the magnetic fields to converge into the atmosphere, resulting in auroral activity.
The detection will help scientists understand how Neptune’s magnetic field interacts with particles streaming out from the Sun. They also measured the temperature of the top of Neptune’s atmosphere for the first time since Voyager 2’s flyby, finding it had cooled by several hundreds of degrees over the years.
This new findings provide insights into Neptune’s atmospheric science and suggest that this region can change greatly despite being far from the Sun. The team plans to study Neptune with Webb over a full solar cycle, which could reveal more about Neptune’s magnetic field and its origin.
Source: https://science.nasa.gov/missions/webb/nasas-webb-captures-neptunes-auroras-for-first-time