Experience the pink glow of Uranus in all its glory in 3D

Experience the pink glow of Uranus in all its glory in 3D

New observations from the James Webb Space Telescope show how vivid auroras emerge through Uranus’ tilted magnetic field.

By Lee Billings edited by Claire Cameron

Among the planets of the solar system, Uranus is criminally neglected. Much like its outer solar system neighbor, Neptune, this “ice giant” world is so far from the sun (and therefore visually bland) that we have only sent one spacecraft, NASA’s Voyager 2, to its destination – and that was more than 40 years ago.

This solitary flyby, carried out at the end of January 1986, practically did not probe the depths of the planet. And it happened right after a solar storm crushed Uranus’ magnetic fieldlimiting what scientists could learn from Voyager 2 observations.

Yet despite its dull appearance, Uranus could be crucial in solving multiple planetary puzzles. It is one of two major planets orbiting the Sun that rotate in a retrograde (clockwise) motion and is the only one with such an extreme axial tilt, in which its axis of rotation is almost perpendicular to its orbital motion. In other words, Uranus moves around our star like a top that tips over and spins backwards. This celestial bias is likely because Uranus was hit by a massive planetary collision early in the solar system’s history, and gives the ice giant strange seasons that span 42 Earth years. This may also have helped create Uranus’ unbalanced and chaotic magnetic field, misaligned with the planet’s center and rotation.

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Yet as strange as Uranus is in some ways, in other ways it seems more typical: Most of the planetary systems that astronomers have discovered around other stars are filled with so many worlds that resemble Uranus in size and mass that this category of planet is probably the most common in the Milky Way. So if we want to understand how planets form and evolve, whether here or throughout the galaxy, we probably need to understand Uranus better.

That’s why new observations of the ice giant by NASA’s James Webb Space Telescope (JWST) offer more than just pretty pictures. Performed by an international team and directed by Paola Tiranti, holder of a doctorate in planetary sciences. student at Northumbria University in England, the observations were published In Geophysical research letters on February 19. Previous JWST observations of the planet have revealed a new moonmapped the subtle rings of the worldand more.

Capture almost a full Uranian daythe new JWST data maps the temperature and density of charged particles moving through the ice giant’s ionosphere, a high region of the atmosphere where auroras form and interact with the solar wind, as well as Uranus’ strange magnetic field. The data, which specifically track the abundance of H₃⁺an ion composed of three hydrogen nuclei, constitutes the best three-dimensional map of the planet’s upper atmosphere.

“Thanks to Webb’s sensitivity, we can track how energy moves upward through the planet’s atmosphere and even see the influence of its unbalanced magnetic field,” Tiranti said in a declaration.

JWST has a good view of how Uranus’ auroras sweep through the lower atmospheric layers, she added. “Webb has now shown us how deep these effects propagate into the atmosphere. By revealing the vertical structure of Uranus in such detail, Webb helps us understand the energy budget of ice giants. This is a crucial step toward characterizing giant planets beyond our solar system.”

One mystery that observations have confirmed but unfortunately not solved concerns Uranus’ particularly plummeting temperature. For decades, scientists have observed that the ice giant’s upper atmosphere was cooling in unexpected ways – and these latest measurements show that trend continuing. JWST observed an average temperature of around 150 degrees Celsius in Uranus’ upper atmosphere, lower than values ​​seen in previous observations.

The planet’s auroras appear as bright pink spots that extend above the visible edges of Uranus’ atmosphere in the JWST images, which also capture the ice giant’s delicate ring system and the bright clouds around its polar cap. But in these images, Uranus’ rings and clouds are mostly just eye candy, says Heidi Hammel, a JWST interdisciplinary scientist at the Association of Universities for Astronomical Research, who was not involved in the work. The auroras are the true scientific stars.

“These aurora detections are extremely important because they are a direct manifestation of the planet’s internal magnetic field,” says Hammel. “We really have no other way to probe the magnetic field remotely without a spacecraft on site.”

American astronomers I still hope send another spaceship to Uranus in the years to comebut tight federal budgets – and the difficult timing required for energy-efficient interplanetary travel – could place such a mission in an uncomfortable future. For now, scientists may have to make do with the distant but breathtaking views of JWST.