Thanks to the study of a planetary aurora with the James Webb Space Telescope, an interesting glow has been found on Neptune. Following studies carried out by Voyager 2 and research by the Hubble Space Telescope, a new path is now opening up. Using the Near-Infrared Spectograph (NIRSped), the James Webb telescope was able to detect the ion H₃⁺, something unusual in a planetary magnetic field. This represents a major advance in the study of solar wind. Read on to learn more.
New unreal cosmic surprises
Some cosmic surprises are so unreal they feel like plot twists from a sci-fi movie. That’s what happened at the time the James Webb Space Telescope (JWST) turned its look toward Neptune, the most far away planet from the Sun. What started as a normal observation turned into the show of a shimmering light show that left astronomers both suprised and scratching their heads — and eager to comprehen every detail under such an amazing display in the far reaches of our solar system.
Neptune’s “impossible colors” are revealed after years of mystery
For many time, investigators imagined that Neptune had auroras, but the key that kept slipping away. Even Voyager 2’s historic flyby in 1989 presented just fragments of proves, never the entire picture. That modifed in June 2023, when the James Webb Space Telescope — with its unmatched infrared vision — at the end brought those elusive lights into focus.
The happening got the nickname “impossible colors” due to the fact that the hues just don’t exist in the range our eyes can detect. They appear thanks to a combination of Hubble’s visible-light imagery and Webb’s spectral data, mapping invisible wavelengths into colors we can see.
“Turns out, actually imaging the auroral activity on Neptune was only possible with James Webb’s near-infrared sensitivity” said Henrik Melin, the lead researcher on the study.
The way auroras dance far from Neptune’s poles
The most interesting twist wasn’t just the color — it was where the lights appeared. On Earth, Jupiter, and Saturn, auroras crown the poles, next to the way of the planet’s magnetic field lines. Neptune breaks the rules: its auroras glow at mid-latitudes, just like they were draped over South America instead of the polar caps.
The culprit is an non-commong tilted and offset magnetic field — skewed about 47 degrees from Neptune’s rotation axis and changed from its center. It’s as if the planet’s “magnetic heart” had been knocked off-balance, funneling charged particles to unknows areas and igniting a glow where it simply shouldn’t be — a cosmic quirk that keeps to puzzle even the most experienced planetary investigators.
The reason of why Neptune’s auroras stayed invisible for so many time
James Webb used its Near-Infrared Spectrograph (NIRSpec) to recgonize the presence of the H₃⁺ ion, a charged molecule that is a “seal of authenticity” for auroras on giant planets. And the understanding of this discovery took so long is directly connected to Neptune’s extreme conditions.
That’s due to the fact of its upper atmosphere is hundreds of degrees colder nowadays than it was when Voyager 2 flew past in 1989. This cooling diminishes the auroras’ luster, making them virtually not visible to less sensitive telescopes. That’s the main reason if it was only with James Webb’s technology that scientists were capable of clearly record the happening (just as he did when he discovered more than 800,000 galaxies in the darkness).
Could Neptune’s strange auroras rewrite what we know about magnetic fields?
This isn’t just a pretty light show — it’s a scientific turning point. The achievement present investigators an opportunity to keep an eye on how tilted magnetic fields interact with the solar wind, follow how the 11-year solar cycle plays out on far-flung worlds, and compare Neptune’s quirks to Uranus, another planet with the same skewed field. Looking forward, scientists want to watch Neptune through an whole solar cycle, mapping changes in auroral activity as the Sun’s magnetism modifications.
These insights will aid shape incoming deep-space missions, since any probe bound for Neptune or Uranus will require infrared-tuned instruments to catch likely happening. And the findings may motive an overhaul of existing magnetic-field models, which not always account for such extreme, unconventional alignments — after all, the missing matter has finally been found floating in space.
