NASA’s James Webb Space Telescope confirms auroras on Neptune for the first time
NASA has captured auroras shining on Neptune, the most distant planet in the solar system. The space agency shared images of the solar phenomenon taken by the James Webb Space Telescope, marking the first time auroras have been confirmed on the icy gas giant.
Sharing the images, NASA wrote, “For the first time, we can see auroras on Neptune – thanks to @NASAWebb.”
“Astronomers had seen hints before, but near-infrared light data confirms Neptune has auroras, like other gas giant planets in our solar system.”
Auroras and their occurrence in the solar system
Auroras occur when solar flares interact with a planet’s magnetic field and strike its upper atmosphere. These vibrant displays are common on Earth, especially during periods of solar maximum.
Scientists have long suspected that Neptune also experiences auroras, but until now, there had been no direct confirmation.
Neptune was the only gas giant without confirmed auroras
When NASA’s Voyager 2 flew by Neptune in 1989, astronomers detected hints of auroral activity. Over the years, auroras have been observed on Jupiter, Saturn, and Uranus. Neptune was the only giant planet where auroras had not been directly confirmed—until now.
The images shared by NASA illustrate how Webb’s view of Neptune differs from that of the Hubble Space Telescope. While Hubble’s data does not show auroras, Webb’s advanced near-infrared capabilities captured them clearly.
Webb’s infrared sensitivity made the discovery possible
Lead author of the study, Henrik Melin of Northumbria University, stated, “Turns out, actually imaging the auroral activity on Neptune was only possible with Webb’s near-infrared sensitivity.”
Conducting his research at the University of Leicester, Melin added, “It was so stunning to not just see the auroras, but the detail and clarity of the signature really shocked me.”
Webb’s Near-Infrared Spectrograph picked up the auroras in 2023. Astronomers measured the temperature of Neptune’s upper atmosphere through a spectral analysis and found a significant emission line indicating the presence of trihydrogen cation (H3+).
H3+—A signifier of auroral activity on gas giants
H3+ is a known indicator of auroral activity on Jupiter, Saturn, and Uranus, leading scientists to expect similar findings on Neptune. “H3+ has been a clear signifier on all the gas giants, and we expected to see the same on Neptune as we investigated the planet over the years,” said Heidi Hammel of the Association of Universities for Research in Astronomy.
“Only with a machine like Webb have we finally gotten that confirmation.”
Auroras on Neptune occur in unusual locations
Unlike on Earth, where auroras occur near the poles, Neptune’s auroras appear at its geographic mid-latitudes, roughly at the same point where South America is located on Earth. This is due to Neptune’s magnetic field being tilted by 47 degrees from its rotation axis, a discovery made by Voyager 2 in 1989.