The James Webb Space Telescope has captured the first-ever bright aurora on Neptune. Astronomers have suspected the planet has this phenomenon in the past, but there has been no confirmation.
NASA writes about this.
Auroras occur when particles from the Sun collide with a planetʼs magnetic field and strike the upper atmosphere. The energy released during these collisions creates the recognizable multi-colored glow.
Astronomers saw hints of aurora on Neptune in 1989 when the Voyager 2
Only the James Webb Space Telescope was able to see the aurora. The telescope transmitted the first data to Earth in 2023. Then, scientists saw in the images a key marker of the aurora — the trihydrogen cation. In the images, the aurora on Neptune looks like turquoise spots.
On the left is an image of Neptune taken by the Hubble Space Telescope. On the right is the same image combined with data from the James Webb Space Telescope. The turquoise spots on Neptuneʼs surface are visible auroras.
The James Webb observations also explain why Neptuneʼs auroras have been elusive for so long. Scientists have found that instead of the poles, they appear in mid-latitudes because Neptuneʼs magnetic field is tilted 47 degrees to its axis of rotation, causing the solar wind to interact differently with the atmosphere.
Using Webbʼs observations, scientists were also able to measure the temperature of Neptuneʼs upper atmosphere for the first time since Voyager 2. It was much lower. Such low temperatures mean that the aurorae (which depend in part on the temperature of the ionized layer of the atmosphere) are much dimmer—which is why they could have gone unnoticed for decades.
Such significant cooling suggests that even in regions very far from the Sun, the atmosphere can undergo major changes. This indicates the presence of complex climatic and magnetic processes that are not yet fully understood.
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