Uranus

The fact that Uranus' magnetic field is tilted to its rotation axis and is offset from its center causes fluctuations of its magnetic field that are associated with the rotation of Uranus' interior. From measurements of these fluctuations by Voyager 2, the rotation period of Uranus' interior was found to be 17 hours 14 minutes. This is the first accurate rotation period for Uranus; earlier attempts in the last 100 years to determine its rotation period from spectroscopic and photometric observations gave very diverse, conflicting, and, as we now know, incorrect results. Other somewhat different rotation periods found from Voyager 2 observations of cloud features in Uranus' atmosphere, which range from 16 to 17.5 hours, are caused by winds in Uranus' atmosphere.