In a major breakthrough, scientists have revised the length of a day on Uranus—and it’s now 28 seconds longer than we thought.
Thanks to over a decade of data from the Hubble Space Telescope, researchers have calculated that a full Uranian day lasts exactly 17 hours, 14 minutes, and 52 seconds.
That may sound like a tiny change, but for planetary scientists, it’s a big deal.
Until now, the only direct measurements came from NASA’s Voyager 2 flyby in 1986, which left lingering uncertainties—especially around Uranus’ magnetic poles. Those outdated rotation estimates made it nearly impossible to accurately track how the planet's magnetosphere behaves over time.
To solve this, a team led by Laurent Lamy (Paris Observatory) analyzed Hubble’s ultraviolet observations from 2011 to 2022, tracking auroras caused by solar wind slamming into Uranus’ magnetic field.
By following those glowing signals, they were able to pinpoint the magnetic poles and determine Uranus’ rotation period with unprecedented precision—even more accurately than we know Jupiter’s.
That’s especially impressive considering Uranus spins almost completely sideways, making these measurements incredibly tricky.
This refined rotation rate is crucial—it will help scientists build better models of Uranus’ interior, magnetic field, and future missions, including NASA’s upcoming plans to explore the ice giant in detail.
RESEARCH PAPER:
L. Lamy et al., “A new rotation period and longitude system for Uranus”, Nature Astronomy (2025)
In a major breakthrough, scientists have revised the length of a day on Uranus—and it’s now 28 seconds longer than we thought.
Thanks to over a decade of data from the Hubble Space Telescope, researchers have calculated that a full Uranian day lasts exactly 17 hours, 14 minutes, and 52 seconds.
That may sound like a tiny change, but for planetary scientists, it’s a big deal.
Until now, the only direct measurements came from NASA’s Voyager 2 flyby in 1986, which left lingering uncertainties—especially around Uranus’ magnetic poles. Those outdated rotation estimates made it nearly impossible to accurately track how the planet's magnetosphere behaves over time.
To solve this, a team led by Laurent Lamy (Paris Observatory) analyzed Hubble’s ultraviolet observations from 2011 to 2022, tracking auroras caused by solar wind slamming into Uranus’ magnetic field.
By following those glowing signals, they were able to pinpoint the magnetic poles and determine Uranus’ rotation period with unprecedented precision—even more accurately than we know Jupiter’s.
That’s especially impressive considering Uranus spins almost completely sideways, making these measurements incredibly tricky.
This refined rotation rate is crucial—it will help scientists build better models of Uranus’ interior, magnetic field, and future missions, including NASA’s upcoming plans to explore the ice giant in detail.
📄 RESEARCH PAPER:
L. Lamy et al., “A new rotation period and longitude system for Uranus”, Nature Astronomy (2025)
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