Scientists using the James Webb Space Telescope just mapped the mysterious upper atmosphere of Uranus for the first time, revealing strange new features of the planet’s mysterious magnetic field and glowing auroras.
The The James Webb Space Telescope (JWST) observed Uranus rotating for 15 hours (almost a full Uranian day) to learn more about how ice giants distribute energy in the upper layers of the atmosphere and to investigate how the planet’s northern lights work.
To learn more, scientists used JWST to study Uranus’ magnetosphere — the region of space around Uranus that is dominated by the planet’s magnetic field.
“Uranus’ magnetosphere is one of the strangest in the solar system,” study lead author Paola Tirantia doctoral student at Northumbria University in the UK, said in a Statement from the European Space Agency (ESA).. “Webb has now shown us how deep these effects reach into the atmosphere.”
Strange lights on Uranus
JWST mapped “the most detailed portrait yet” of how particles in Uranus’ upper atmosphere are energized (ionized) by interactions with the sun, ESA officials said in the statement. The study, published February 19 in the journal Geophysical Research Lettersaimed to measure ion temperature and density as far as 3,100 miles (5,000 kilometers) above the cloud tops of Uranus.
Temperature and density do not peak at the same height, JWST showed. Ions were hottest between about 2,500 and 3,100 miles (4,000 and 5,000 km), but densest at about 600 miles (1,000 km). This is because of the “complex geometry” of the planet’s magnetic field, ESA officials said in the statement.
That geometry also produced two bright bands of auroras near Uranus’ magnetic poles. Between the auroral belts, however, there is a “depletion” in both ion density and auroral emission — an effect likely produced by transitions between the planet’s magnetic field lines, the researchers said. Observations of Jupiter’s upper atmosphere have shown similar transition regions.
In addition to mapping Uranus’ upper atmosphere in three dimensions for the first time, JWST confirmed findings from previous studies that suggested the planet’s upper atmosphere has been cooling steadily since the early 1990s. The telescope showed that the average temperature of Uranus’ atmosphere is about 307 degrees Fahrenheit (153 degrees Celsius), which is lower than temperature measurements from other spacecraft and ground-based telescopes.
“By revealing the vertical structure of Uranus in such detail, Webb is helping us understand the energy balance of the ice giants,” Tiranti said. “This is a crucial step towards characterizing giant planets outside our solar system.”
Brandon Spector
The only planet to orbit the sun sideways, Uranus is a literal weirdo. Close-up observations are limited to a single 1986 flyby by Voyager 2, leaving much to be discovered from a distance. One of JWST’s main missions is to study the atmospheres of the Solar System’s planets in infrared light, providing new clues to how our neighboring worlds formed – and whether alien star systems may follow similar paths. Ultimately, understanding giant planets like Uranus will help scientists discover potentially habitable worlds around distant stars.
Tiranti, PI, Melin, H., Moore, L., Thomas, EM, Knowles, KL, Stallard, TS, Roberts, K., & O’Donoghue, J. (2026). JWST discovers the vertical structure of Uranus’ ionosphere. Geophysical Research Letters, 53(4). https://doi.org/10.1029/2025gl119304
