Webb telescope reveals Uranus’ upper atmosphere in unprecedented detail
The James Webb Space Telescope delivers the 1st detailed 3D map of Uranus’s upper atmosphere, revealing dramatic temperature shifts and glowing auroras.
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NASA’s James Webb Space Telescope has captured the first vertical view of Uranus’s upper atmosphere, delivering an unprecedented look at the planet’s ionosphere and auroral structures.
The new observations, released by NASA on Tuesday, show how temperature and charged particles vary with height above the ice giant’s cloud tops, offering fresh insight into one of the least understood worlds in the solar system.
For decades, Uranus has remained enigmatic to scientists. Its upper atmosphere, composed mostly of hydrogen and helium and extending thousands of miles above the cloud layer, has been challenging to study since the only spacecraft to fly by the planet, Voyager 2 in 1986, provided limited data, according to the European Space Agency. Webb’s Near-Infrared Spectrograph (NIRSpec) changed that by observing the planet over nearly a full rotation.
A collage of 3D images of Uranus showing the vertical structure of the planet's upper atmosphere taken by the James Webb Space Telescope's NIRSpec instrument. (Image credit: ESA/Webb, NASA, CSA, STScI, P. Tiranti, H. Melin, M. Zamani (ESA/Webb)
The resulting three-dimensional map reveals how temperatures peak between roughly 1,800 to 2,500 miles above the cloud tops, while the density of electrically charged ions is highest around 621 miles. These vertical profiles give astronomers a clearer picture of how energy moves through the upper atmosphere and interacts with the magnetic field.
“This is the first time we’ve been able to see Uranus’s upper atmosphere in three dimensions,” said Paola Tiranti, of Northumbria University, 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.”
A collage of 3D images of Uranus showing the vertical structure of the planet's upper atmosphere taken by the James Webb Space Telescope's NIRSpec instrument. (Image credit: ESA/Webb, NASA, CSA, STScI, P. Tiranti, H. Melin, M. Zamani (ESA/Webb)
Webb also traced bright auroras shaped by Uranus’s unusually tilted and offset magnetic field, which causes charged particles to swirl in complex patterns unlike those seen at Earth or Jupiter. These auroras light up the upper layers where the magnetic field funnels energetic particles into the atmosphere.
“Uranus’s magnetosphere is one of the strangest in the Solar System,” Tiranti said. “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."
A view of the backside of Icehotel 34 with the Northern Lights or Aurora Borealis over it on December 16, 2023, in Jukkasjarvi, Sweden. Since 1989, the Icehotel - part hotel, part art exhibition - has been crafted annually from ice taken from the Torne River. (Photo by Roy Rochlin/Getty Images)
Additionally, the new data confirm that Uranus’s upper atmosphere has continued cooling over the past three decades, a trend first noted in the early 1990s. Understanding this cooling and energy distribution is essential not just for studying Uranus but also for interpreting observations of ice giant exoplanets beyond our solar system.
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