Hubble Gives Us an Accurate Measurement for Uranus's Day Length

It’s easy to measure the rotation rate of terrestrial planet by tracking surface features but the gas and ice giants pose more of a problem. Instead, previous studies have relied upon indirect measures like measuring the rotation of their magnetic fields. Now a team of astronomers have used the Hubble Space Telescope to refine the rotation rate of Uranus with an incredible level of accuracy. This time though, instead of studying the rotation of the magnetic field, they tracked aurora to measure one rotation!