Overview
- The peer-reviewed study was published on February 19, 2026 in Geophysical Research Letters.
- Using NIRSpec’s Integral Field Unit, Webb observed Uranus for 15 hours on January 19, 2025 under GO program 5073 led by Henrik Melin.
- The mapping resolves the ionosphere to about 5,000 kilometers above the clouds, with ion densities peaking near 1,000 kilometers and temperatures peaking between 3,000 and 4,000 kilometers.
- Two auroral bands were detected near the magnetic poles with a clear depletion between them, a pattern linked to transitions in Uranus’s unusually tilted and offset magnetic field.
- Webb measured an average upper-atmosphere temperature of roughly 426 kelvins, confirming a cooling trend that has persisted since the early 1990s and informing models of ice-giant and exoplanet atmospheres.