Uranus' Rotation Recalculated: Hubble Telescope Reveals a Longer Day

 

A recent study using observations from the Hubble Space Telescope has revealed that a day on Uranus is slightly longer than previously estimated.

 The fresh analysis shows that the ice giant takes **17 hours, 14 minutes, and 52 seconds** to complete a full rotation—**28 seconds longer** than NASA's Voyager 2 spacecraft had originally measured nearly four decades ago.  

Voyager 2, the first and only spacecraft to visit Uranus, flew past the planet in January 1986 and calculated its rotation period at **17 hours, 14 minutes, and 24 seconds**. 

This estimate was based on radio signals emitted by Uranus' auroras and direct measurements of its magnetic field. These findings were essential in constructing coordinate maps of the distant world, but a new study suggests that some of these maps may now require revision.  

Unraveling Uranus' Magnetic Mystery  

The original estimate carried uncertainties that led to a **180-degree error** in Uranus’ longitude, making the orientation of its magnetic axis unreliable just a few years after Voyager 2's flyby. 

This issue affected the accuracy of coordinate systems dependent on the outdated rotation period.  

To resolve this problem, a team of astronomers led by Laurent Lamy from the Paris Observatory analyzed **Hubble Space Telescope data spanning more than a decade, from 2011 to 2022**. By tracking the motion of Uranus' auroras over time, they were able to pinpoint the planet's magnetic poles with greater precision, leading to a more accurate rotation period.  

"The continuous observations from Hubble were crucial," said Lamy. "Without this wealth of data, it would have been impossible to detect the periodic signal with the level of accuracy we achieved."  

 A New Method for Studying Exoplanets  

This innovative approach could be applied to determine the rotation rates of other celestial bodies, particularly those with magnetic fields and auroras—including exoplanets in distant star systems. 

By using long-term observations and tracking auroral movements, scientists may soon unlock the mysteries of planetary rotations beyond our solar system.  

As space exploration continues to advance, new discoveries like this remind us that even seemingly well-understood worlds can still hold surprises. 

With more precise measurements, astronomers are now better equipped to map and study Uranus, ensuring that future missions will navigate its enigmatic terrain with greater accuracy.