For the first time, astronomers have got real-time view at the edge of the Solar System as the James Webb Space Telescope has mapped the vertical structure of Uranus’s upper atmosphere in unprecedented detail.
This breakthrough offers Earth its inaugural real-time glimpse into the ice giant’s ionosphere, revealing how temperature, charged particles, and auroras vary with altitude.
Uranus is the seventh planet from the Sun and an ice giant known for its striking blue-green color, caused by methane in its atmosphere. It rotates on its side with a 98-degree tilt, creating extreme seasons. Uranus has faint rings and 27 known moons, including Titania and Oberon.
WHAT DID JAMES WEBB TELESCOPE SEE ON URANUS?
An international team led by Paola Tiranti from Northumbria University in the UK used JWST’s NIRSpec instrument to observe Uranus for nearly a full rotation on January 19, 2025.
Over 15 hours from Webb’s orbit, they captured faint glows from molecules up to 5,000 kilometers above the cloud tops.
Temperatures peak between 3,000-4,000 km at around 153°C, while ion densities maximise near 1,000 km, showing clear longitudinal variations tied to the planet’s oddly tilted magnetic field.
“This is the first time we’ve been able to see Uranus’s upper atmosphere in three dimensions,” Tiranti said. “With Webb’s sensitivity, we can trace how energy moves upward and see the influence of its lopsided magnetic field.”
The data spotlight two bright auroral bands near the magnetic poles, plus a depleted emission zone between them, echoing features at Jupiter where magnetic geometry channels particles.
Uranus’s magnetosphere, tilted and offset from its rotation axis, creates sweeping auroras that sculpt the atmosphere uniquely.
Webb confirms the upper atmosphere’s ongoing cooling since the 1990s, with temperatures lower than prior ground or space-based measures. This trend hints at energy loss dynamics in ice giants, aiding models for exoplanets.
Part of JWST General Observer program 5073, the research appears in Geophysical Research Letters. It demystifies Uranus’s “strangest” magnetosphere, advancing ice giant science and energy balance insights for distant worlds.
These findings mark a pivotal step in planetary exploration, blending real-time spectroscopy with 3D mapping for future discoveries.
