James Webb Space Telescope Maps Uranus's Upper Atmosphere and Auroras

The James Webb Space Telescope (JWST) has produced the first three-dimensional map of Uranus's upper atmosphere, offering new insights into the planet's auroras and magnetic field. Over a 15-hour observation period, nearly covering a full Uranian rotation, JWST's Near-Infrared Spectrograph (NIRSpec) detected faint emissions from molecules high above the cloud tops.

The study, led by Paola Tiranti of Northumbria University, measured temperatures and ion densities up to 5,000 kilometers above Uranus's clouds. Findings indicate that temperatures peak between 3,000 and 4,000 kilometers altitude, while ion densities are highest around 1,000 kilometers. These variations are influenced by Uranus's uniquely tilted magnetic field, which is offset from the planet's rotation axis.

The observations also revealed two bright auroral bands near the magnetic poles, with a region of reduced emissions between them. This pattern is likely due to transitions in the planet's magnetic field lines, similar to features observed on Jupiter.

Additionally, the data confirm a continued cooling trend in Uranus's upper atmosphere since the early 1990s, with current average temperatures around 426 kelvins (approximately 153 degrees Celsius). This cooling trend provides valuable information on the energy balance of ice giant planets.

These findings enhance our understanding of Uranus's atmospheric dynamics and may inform studies of similar exoplanets beyond our solar system.