Conversation

It's easy to measure the rotation rate of terrestrial planets, but the gas and ice giant planets are much more difficult, where you can't measure features on their surface directly. Instead, astronomers have relied on indirect methods, like measuring the rotation of their magnetic fields. New observations from Hubble have refined the rotation rate of Uranus with unprecedented precision, using an extremely clever method: watching the auroras complete one rotation.

https://www.esa.int/ESA_Multimedia/Images/2025/04/Hubble_helps_determine_Uranus_rotation_rate_with_unprecedented_precision