NASA's Webb Telescope Reveals First Look at Neptune's Aurora — Leading to a New Mystery
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03/27/2025 12:04 PM
Experts are not sure why Neptune's auroras can be seen around the planet's "mid-latitudes," and not the north and south poles
NASA, ESA, CSA, STScI, Heidi Hammel (AURA), Henrik Melin (Northumbria University), Leigh Fletcher (University of Leicester), Stefanie Milam (NASA-GSFC)
At the left, an enhanced-color image of Neptune from NASA's Hubble Space Telescope. At the right, that image is combined with data from NASA's James Webb Space Telescope.NASA's James Webb space telescope is offering a new look at Neptune's aurora, leading to a new mystery involving the eighth planet from the sun.
According to an article published by NASA on Wednesday, March 26, the Webb telescope "captured bright auroral activity on Neptune" for the very first time in June 2023.
Despite "successful detections" on Jupiter, Saturn and Uranus, astronomers had yet to confirm or obtain images of Neptune's aurora until nearly two years ago, when Webb's Near-Infrared Spectrograph acquired the data.
"Neptune was the missing piece of the puzzle when it came to detecting auroras on the giant planets of our solar system," NASA said.
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Henrik Melin, who conducted the research while at the University of Leicester in England, said that "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 Melin, the lead author of an article about the researching surrounding the aurora published in Nature Astronomy.
Auroras appear when energetic particles "strike the upper atmosphere" after getting trapped in a planet's magnetic field, according to NASA.
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Neptune's aurora "appears as splotches represented in cyan," the agency said. But it is "noticeably different" from what is seen on other planets, including Earth.
The auroras "are located at the planet's geographic mid-latitudes," rather than at the north and south poles, "due to the strange nature of Neptune's magnetic field."
Now, astronomers have a new mystery on their hands. They hope to study Neptune's next full solar cycle, which lasts about 11 years, in hopes of learning more about the planet's magnetic field.
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Additionally, experts learned that Neptune's upper atmosphere had cooled "by several hundreds of degrees" between 1989 and 2023, Melin said.
Cooler temperatures lead to dimmer auroras, according to NASA. This could explain why Neptune's auroras were concealed for so long.
Leigh Fletcher of Leicester University, co-author on the Nature Astronomy article about Neptune's auroras, said experts now have a better understanding of what is needed to study the planet.
"We now know how important it will be to have instruments tuned to the wavelengths of infrared light to continue to study the auroras," he explained.
