Overview
- Using JWST’s NIRSpec Integral Field Unit, researchers observed Uranus for nearly a full 15‑hour rotation on 19 January 2025 and mapped up to 5,000 kilometers above the cloud tops.
- Temperatures peak between roughly 3,000 and 4,000 kilometers while ion densities peak near 1,000 kilometers, with an average temperature of about 426 K that is lower than prior measurements.
- Webb data confirm a multi‑decade cooling trend in Uranus’s upper atmosphere first noted in the early 1990s.
- Two bright auroral bands appear near the magnetic poles with a depleted region between them, features linked to the planet’s highly tilted and offset magnetic field and its changing field lines.
- The peer‑reviewed study, led by Paola Tiranti under JWST GO program 5073 (PI Henrik Melin) and published in Geophysical Research Letters, provides a first vertical view of the ionosphere and includes a timelapse spanning nearly one Uranian day.