A research team has successfully created the first-ever three-dimensional map of Uranus\u2019s upper atmosphere. This reveals how the ice giant\u2019s unusual magnetic field shapes spectacular auroras high above the planet\u2019s clouds.<\/p>\n
The team led by Paola Tiranti observed Uranus for nearly a full rotation, detecting the faint glow from molecules up to 3,100 miles (5,000 kilometres) above the cloud tops.<\/p>\n
The observations provide the most detailed picture yet of where the planet\u2019s auroras form and how energy moves through its atmosphere.<\/p>\n
Auroras occur when energetic particles become trapped in a planet\u2019s magnetic field and strike the upper atmosphere, releasing energy<\/a> that creates a signature glow.<\/p>\n The team found that the temperatures peak between 3,000 and 4,000 kilometres above the cloud tops, whilst ion densities reach their maximum around 1,000 kilometres.<\/p>\n The team confirms that Uranus\u2019 upper atmosphere has continued to cool over the past thirty years \u2013 a trend that has been surprising scientists<\/a> for over three decades.<\/p>\n Using Webb\u2019s Near-Infrared Spectrograph, the team mapped out the temperature and density of ions in Uranus\u2019s ionosphere, a region where the atmosphere becomes ionised and interacts strongly with the planet\u2019s magnetic field.<\/p>\n For first time, researchers were able to see Uranus\u2019s upper atmosphere in three dimensions<\/p>\n \u201cThis is the first time we\u2019ve been able to see Uranus\u2019s upper atmosphere in three dimensions. With Webb\u2019s sensitivity, we can trace how energy moves upward through the planet\u2019s atmosphere and even see the influence of its lopsided magnetic field,\u201d said lead author Paola Tiranti.<\/p>\n Uranus\u2019 magnetosphere is one of the strangest in the Solar System. Unlike Earth, where the magnetic field is relatively aligned with the planet\u2019s rotation axis, Uranus\u2019s magnetic field is tilted by nearly 60 degrees and offset from the planet\u2019s centre. This means its auroras sweep across the surface in complex ways, according to researchers.<\/p>\n Webb observations detected two bright auroral bands<\/p>\n The Webb observations detected two bright auroral bands near Uranus\u2019s magnetic poles, together with a distinct depletion in emission and ion density between them \u2013 a feature likely linked to how magnetic field lines guide charged particles through the atmosphere. Similar darkened regions have been seen at Jupiter, where magnetic field geometry controls particle flow, according to<\/a> a press release.<\/p>\n \u201cBy revealing Uranus\u2019s 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,\u201d said Tiranti.<\/p>\n