Astronomers have mapped the vertical structure of Uranus's upper atmosphere for the first time ever, and have produced a video showing the gas giant rotating on its axis.
A team of researchers used the James Webb Space Telescope to observe Uranus for nearly one full rotation, detecting and mapping the glow of molecules above the planet's clouds.
More on Uranus
This is the most detailed view astronomers have ever got of the regions where aurora displays form on Uranus and reveals how they're influenced by the planet's strange magnetic field.
The study is also showing how Uranus's atmosphere has cooled over the past three decades.
A new view of Uranus's atmosphere
"This is the first time we’ve been able to see Uranus’s upper atmosphere in three dimensions," says Paola Tiranti of Northumbria University in the United Kingdom, who led the study.
"With Webb’s sensitivity, we can trace how energy moves upward through the planet’s atmosphere and even see the influence of its lopsided magnetic field."
The team used Webb to map the temperature and density of ions – charged particles – as high as 5,000km (3,100 miles) above Uranus's atmosphere.
At this height, in a region called the ionosphere, the planet's the atmosphere becomes ionised and interacts with the magnetic field.
The team found that Uranus's atmospheric temperatures peak between 3,000 and 4,000km (1,860 and 2,485 miles), and ion densities reach their maximum around 1,000 kilometres (620 miles) up.
This shows clear height variations within the atmosphere, which the team say is related to the ice giant's magnetic field.
And the astronomers were also able to confirm that Uranus's atmosphere cooling down; something that has been recorded since the 1990s.
Webb found an average temperature of around 150°C (300°F), which is lower than temperatures recorded by ground-based telescopes or previous spacecraft.
Aurora displays on Uranus
Webb also detected two bands of bright aurora near Uranus's magnetic poles.
The team say they found a lack of emission and ion density in part of the region between two bands, and that this is related to Uranus's magnetic field lines.
"Uranus’s magnetosphere is one of the strangest in the Solar System," says Tiranti.
"It’s tilted and offset from the planet’s rotation axis, which means its auroras sweep across the surface in complex ways.
"Webb has now shown us how deeply those effects reach into the atmosphere. By revealing Uranus’s vertical structure in such detail, Webb is helping us understand the energy balance of the ice giants.
"This is a crucial step towards characterising giant planets beyond our Solar System."
The study was published in the Geophysical Research Letters.
