Webb gets the first view of Uranus’ upper atmosphere

Uranus is a giant icy planet with one of the strangest magnetic fields in the solar system. Unlike the Earth, it is tilted, off-center, and does not completely align with the planet’s rotation. Using Webb’s NIRSpec instrument (Near-Infrared Spectrograph), scientists have been able to visualize the upper region of the planet, called the ionosphere. The ionosphere is a high-altitude layer, up to 5,000 km above above Uranus’ cloud tops, where gases are ionized. There are strong interactions with the planet’s magnetic field, which were captured as faint glows in infrared light.

Auroral bands are formed when charged particles follow magnetic field lines. They collide with gases in the upper atmosphere, causing them to glow. Near the magnetic poles, two bright auroral bands were detected with a darker region where emission and ion density were weaker. This could be due to a change in charged particle movement and magnetic field line transitions. Similar patterns were observed on Jupiter.

This discovery is important in understanding how magnetic fields influence planetary atmospheres. It also gives insights into how ice giants like Uranus work, helping us better interpret and understand distant exoplanets.