James Webb Space Telescope (JWST) data has allowed researchers to map Uranus’s upper atmosphere in three dimensions for the first time, showing how charged particles and temperatures vary with altitude.
JWST’s infrared NIRSpec instrument captured almost an entire 17-hour Uranus rotation, recording the planet’s glowing molecules floating above its clouds. The paper, published in Geophysical Research Letters, not only illuminates a part of our solar system but also provides new context for how energy is distributed on ice giants throughout the universe.
Uranus Through the James Webb Space Telescope
“This is the first time we’ve been able to see Uranus’s upper atmosphere in three dimensions,” said lead author Paola Tiranti of Northumbria University. “With Webb’s sensitivity, we can trace how energy moves upward through the planet’s atmosphere and even see the influence of its lopsided magnetic field.”
Data collected by JWST over a 15-hour period stretched up to 5000 kilometers above Uranus’s cloud layer. The team was focused on the ionosphere, the region where the atmosphere becomes ionized and interacts powerfully with the ice giant’s magnetic field. Their work is the most detailed understanding ever assembled of the planet’s upper atmosphere.
JWST Observes Temperatures on an Ice Giant
Activity across elevations observed in the new Webb data is not evenly distributed between temperature and ionization; temperatures peak between 3,000 and 4,000 kilometers, while ionization peaks at only 1,000 kilometers. The researchers say this is due to complexities in the ice giant’s magnetic field geometry.
Unlike Earth, where the magnetic field aligns with the planet’s rotation axis, on Uranus, the magnetic field is 60° off the center.
The NIRSpec results revealed temperatures and ion density in the ionosphere, along with new insights into the atmosphere’s cooling over the last three decades. The cooling trend confirmed in recent James Webb readings dates back to the 1990s, with a new low of 150°C compared to previous data collected by other platforms.
Magnetic Driven Auroras on Uranus
Near the ice giant’s magnetic poles, NIRSpec detected two bright auroral bands. The data shows how Uranus’s tilted magnetic field shapes its auroras, increasing researchers’ understanding of the mechanisms behind these atmospheric light shows.
Intriguingly, JWST also detected a low-emission, low-ion region between the bands, similar to the dark regions observed on Jupiter. On both planets, researchers suspect that magnetic field lines are responsible for these bands, determining how charged particles travel through the upper atmosphere.
“Uranus’s magnetosphere is one of the strangest in the Solar System,” Tiranti explained. “It’s tilted and offset from the planet’s rotation axis, which means its auroras sweep across the surface in complex ways.”
“Webb has now shown us how deeply those effects reach into the atmosphere,” Tiranti added. “By revealing Uranus’s vertical structure in such detail, Webb is helping us understand the energy balance of the ice giants.
“This is a crucial step towards characterising giant planets beyond our Solar System,” Tiranti said.
The paper, “JWST Discovers the Vertical Structure of Uranus’ Ionosphere,” appeared in Geophysical Research Letters on February 19, 2026.
Ryan Whalen covers science and technology for The Debrief. He holds an MA in History and a Master of Library and Information Science with a certificate in Data Science. He can be contacted at ryan@thedebrief.org, and follow him on Twitter @mdntwvlf.