It Took Scientists 11 Years, But They've Finally Figured Out How Long a Day on Uranus Is

The duration of the day impacts many natural processes of Earth. This is not true just for Earth but also for other planets. Therefore, astronomers are always on the lookout for clues that would help them determine the rotation speed of all the planets in the solar system. Recent findings have changed their estimation of the day duration for one of these planets, stated Live Science. These findings have been explained in Nature Astronomy.

The planet in question is Uranus, which, before this study, was thought to have a day that lasted 17 hours, 14 minutes, and 24 seconds. This estimation was done through data garnered by Voyager 2 around four decades ago. This data involved radio signals detected from the planet's auroras as well as insights about the planet's magnetic field. The determined duration was used by experts to ascertain a coordinate system for Uranus.

The estimation altered when a team of researchers examined observations made by the Hubble Space Telescope over eleven years. This data indicated that Uranus' day was possibly 28 seconds longer than previous calculations. This was not surprising to the astronomers, as previous calculations were made taking into consideration an inherent uncertainty of about 36 seconds. It was this uncertainty that made researchers reexamine Uranus' rotation period.

As decades went on, it became hard for experts to keep the uncertainty in mind and determine aspects like Uranus' magnetic axis orientation. "Our measurement not only provides an essential reference for the planetary science community but also resolves a long-standing issue: previous coordinate systems based on outdated rotation periods quickly became inaccurate, making it impossible to track Uranus' magnetic poles over time," explained astrophysicist Laurent Lamy of the Paris Observatory, stated Science Alert.

For the examination, the researchers focused on six sets of Hubble observations taken between 2011 and 2022, stated Live Science. From these sets, astronomers monitored the movement of auroras present on the planet's magnetic poles. The analysis indicated that a day in Urnaus lasts 17 hours, 14 minutes, and 52 seconds. Researchers further claimed that in this calculation, the uncertainty is 0.04 seconds less than what was in the previous assertion. This implies that it has a higher probability of being accurate. 

Researchers cited the importance of the Hubble telescope and the years' worth of data they got from it for the examination. "The continuous observations from Hubble were crucial," Lamy shared. "Without this wealth of data, it would have been impossible to detect the periodic signal with the level of accuracy we achieved." The team believes that this new calculation will remain viable enough to determine several aspects associated with Uranus for decades. "It's not so much that it's changed," Tim Bedding, an astronomer at the University of Sydney in Australia, shared. "It's now accurate enough to be more useful."

Experts think that this estimate will allow them to determine the correct entry points for astronauts in the next Uranus mission. "With this new longitude system, we can now compare auroral observations spanning nearly 40 years and even plan for the upcoming Uranus mission," Lamy said.