James Webb Telescope Maps Uranus’s Atmosphere in 3D, Revealing Auroral Secrets

For the first time, scientists have created a three-dimensional map of Uranus’s upper atmosphere, offering unprecedented insights into the ice giant’s auroras and the strange dynamics of its magnetic field. Detailed observations from the James Webb Space Telescope (JWST) are beginning to unravel the mysteries of this distant planet.

Unveiling Uranus’s Upper Atmosphere

An international team of astronomers observed Uranus for nearly one full rotation – approximately 15 hours – using JWST’s Near-Infrared Spectrograph (NIRSpec) instrument. This allowed them to capture faint molecular emissions in the upper atmosphere, previously difficult to detect. The research, published on February 19 in the journal Geophysical Research Letters, aims to understand how energy is distributed in Uranus’s highest atmospheric layers and how its auroras form and move. Source

Key Findings: Temperature and Ion Density

The team, led by Paola Tiranti of Northumbria University in the United Kingdom, measured temperature and ion density up to 5,000 kilometers above Uranus’s cloud tops, within the ionosphere – the region where the atmosphere becomes ionized and strongly influenced by the planet’s magnetic field. Source Key findings include:

• Highest temperatures were found at an altitude of around 3,000–4,000 kilometers above the clouds.
• The highest ion density was observed at approximately 1,000 kilometers.
• The hottest ions were detected between 4,000–5,000 kilometers.

This difference in the location of temperature and density peaks is attributed to the complex and unusual geometry of Uranus’s magnetic field. Source

Uranus’s Unique Magnetic Field

Uranus is known for its eccentric characteristics, including a nearly 98-degree axial tilt (appearing to roll around the Sun) and a magnetic field tilted 60 degrees from its geographic poles and not aligned with the planet’s center. Source

“Uranus’s magnetosphere is one of the strangest in the Solar System,” said Paola Tiranti. “The magnetic field is tilted and shifted from the planet’s rotational axis, so its aurora sweep across the surface in complex ways. Webb has now shown how deep that influence reaches into the atmosphere.” Source

Auroral Observations

JWST observations revealed two bright auroral bands near Uranus’s magnetic poles. Between these bands lies a ‘depletion’ region – an area of reduced ion density and light emission. Source The telescope also observed bright auroral bands (in white) near the planet’s magnetic poles during a 15-hour observation period in January 2025. Source

Implications for Ice Giant Research

This research marks an important milestone in the study of ice giant planets and provides a foundation for understanding similar planets outside our Solar System. Source By mapping Uranus’s upper atmosphere in 3D, scientists are gaining crucial insights into the energy distribution and atmospheric processes of these enigmatic worlds.