For the first time, the James Webb Space Telescope has imaged the upper atmosphere of Uranus. Webb observed the planet for a full day, measuring temperature and ion concentration as a function of altitude and detecting bright aurorae influenced by Uranus’s strongly tilted magnetic field. These results confirm that the atmosphere of Uranus is still cooling, suggesting it is changing over a long timescale.
Webb’s 3D Map of Uranus’s Atmosphere
According to ESA, astronomers used Webb’s infrared spectrograph to watch Uranus rotate for 15 hours, mapping its layers in 3D and tracing temperature and charged-particle (ion) densities up to 5,000 km above the clouds. Temperatures peak around 3,000–4,000 km and ion density peaks near 1,000 km.
The vertical profile pinpoints where Uranus’s auroras light up in the ionosphere. Two bright auroral bands were seen near the magnetic poles, with a dark gap between – a pattern also seen on Jupiter.
Unusual Magnetic Field and Auroras
Uranus exhibits a magnetic field which is observed to be tilted at 60 degrees from its rotational axis while existing outside of its central point. The planet Uranus, which rotates with its poles facing towards the ground, displays auroras which move through its middle regions, which differs from the way Earth shows its polar lights.
The Webb map shows that Uranus has a magnetosphere, which scientists consider one of the most unusual magnetospheres found in the Solar System because it shows the extent of its tilted magnetic field, which goes into the planet’s atmosphere.
Astronomers will use Webb’s 3D Uranus map to study distant ice giant planets which exist beyond our solar system while they develop better methods to understand planetary climatic systems.
