For the first time, scientists have created a detailed map of the upper atmosphere of Uranus, revealing how temperature and electrically charged particles change with height above the planet.
The breakthrough was made by an international team of astronomers using the powerful James Webb Space Telescope, which observed Uranus for nearly one full rotation and captured faint light emitted by molecules far above its clouds.
Uranus is one of the most unusual planets in our solar system. It spins on its side and has a magnetic field that is both tilted and offset from its center.
These odd features make its atmosphere and auroras—glowing lights caused by charged particles—very different from those on other planets.
By using Webb’s Near-Infrared Spectrograph (NIRSpec), researchers were able to examine a region stretching up to 5,000 kilometers above the cloud tops, known as the ionosphere.
This is where the atmosphere becomes electrically charged and strongly influenced by the magnetic field.
The observations show that temperatures in Uranus’s upper atmosphere reach their highest point between about 3,000 and 4,000 kilometers above the clouds.
Meanwhile, the greatest concentration of charged particles occurs lower down, around 1,000 kilometers.
These patterns vary across the planet, reflecting the strange shape and orientation of Uranus’s magnetic field.
The data also revealed two bright bands of auroras near the magnetic poles. Between them lies a darker region with fewer charged particles, likely caused by changes in the magnetic field lines that guide particles through the atmosphere.
Similar features have been seen on Jupiter, suggesting that magnetic fields play a major role in shaping how energy flows through giant planets.
Another important discovery is that Uranus’s upper atmosphere has continued to cool over the past three decades. The team measured an average temperature of about 426 kelvins (around 150 degrees Celsius), which is lower than earlier estimates from ground-based telescopes and past spacecraft. This long-term cooling trend could help scientists better understand how ice giants lose heat over time.
Researchers say these findings provide the clearest picture yet of Uranus’s upper atmosphere in three dimensions. By tracing how energy moves upward and how the magnetic field affects the planet, the study offers valuable clues about how ice-giant planets work. This knowledge could also help astronomers interpret observations of similar planets orbiting other stars.
The study, led by Paola Tiranti of Northumbria University in the United Kingdom, was published in the journal Geophysical Research Letters. It is based on data collected by Webb on January 19, 2025, during a 15-hour observation campaign. Scientists believe this is only the beginning of what the telescope will reveal about the solar system’s most mysterious worlds.
Source: KSR.
