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\t\t\t\t\t\t19\/02\/2026<\/span> For the first time, an international team of astronomers have mapped the vertical structure of Uranus\u2019s upper atmosphere, uncovering how temperature and charged particles vary with height across the planet. Using\u00a0NASA\/ESA\/CSA James Webb Space Telescope’s NIRSpec instrument, the team observed Uranus for nearly a full rotation, detecting the faint glow from molecules high above the clouds. The results offer a new window into how ice-giant planets distribute energy in their upper layers.<\/p>\n<\/div>\n Led by Paola Tiranti of Northumbria University in the United Kingdom, the study mapped out the temperature and density of ions in the atmosphere extending up to 5000 km above Uranus\u2019s cloud tops, a region called the ionosphere where the atmosphere becomes ionised and interacts strongly with the planet\u2019s magnetic field. These unique data provide the most detailed portrait yet of where the planet\u2019s auroras form, how they are influenced by its unusually tilted magnetic field, and how Uranus\u2019s atmosphere has continued to cool over the past three decades.\u00a0The measurements show that temperatures peak between 3000 and 4000 km, while ion densities reach their maximum around 1000 km, revealing clear longitudinal variations linked to the complex geometry of the magnetic field.<\/p>\n \u201cThis is the first time we\u2019ve been able to see Uranus\u2019s upper atmosphere in three dimensions,\u201d\u00a0said Paola.\u00a0\u201cWith Webb\u2019s sensitivity, we can trace how energy moves upward through the planet\u2019s atmosphere and even see the influence of its lopsided magnetic field.\u201d<\/p>\n Webb\u2019s data confirm that Uranus\u2019s upper atmosphere is still cooling, extending a trend that began in the early 1990s. The team measured an average temperature of around 426 kelvins (about 150 degrees Celsius), lower than values recorded by ground-based telescopes or previous spacecraft.<\/p>\n Two bright auroral bands were detected near Uranus\u2019s magnetic poles, together with a distinct depletion in emission and ion density in part of the region between two bands (a feature likely linked to transitions in magnetic field lines). Similar darkened regions have been seen at Jupiter, where the geometry of the magnetic field there controls how charged particles travel through the upper atmosphere.<\/p>\n \u201cUranus\u2019s magnetosphere is one of the strangest in the Solar System,\u201d\u00a0added Paola.\u00a0\u201cIt\u2019s tilted and offset from the planet\u2019s 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. By revealing Uranus\u2019s 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.\u201d<\/p>\n The study is based on data from JWST General Observer programme\u00a05073\u00a0(PI: H. Melin of Northumbria University in the United Kingdom), which used\u00a0NIRSpec\u2019s Integral Field Unit on 19 January 2025 to observe Uranus for 15 hours. The research has been published in the\u00a0Geophysical Research Letters<\/i>.<\/p>\n<\/p><\/div>\n More information<\/b><\/p>\n Webb\u00a0is the largest, most powerful telescope ever launched into space. Under an international collaboration agreement, ESA provided the telescope\u2019s launch service, using the Ariane 5 launch vehicle. Working with partners, ESA was responsible for the development and qualification of Ariane 5 adaptations for the Webb mission and for the procurement of the launch service by Arianespace. ESA also provided the workhorse spectrograph\u00a0NIRSpec\u00a0and 50% of the mid-infrared instrument\u00a0MIRI, which was designed and built by a consortium of nationally funded European Institutes (The MIRI European Consortium) in partnership with JPL and the University of Arizona.<\/p>\n Webb is an international partnership between NASA, ESA and the Canadian Space Agency (CSA).<\/p>\n Science paper<\/p>\n Release on esawebb.org<\/p>\n \u00a0<\/p>\n \nContact:<\/b>
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