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New Insights into Uranus’ Rotation from Hubble Observations

An international consortium of astronomers, utilizing the NASA/ESA Hubble Space Telescope, has achieved groundbreaking measurements of Uranus’ interior rotation rate through an innovative technique. This advancement boasts an accuracy that is 1,000 times greater than prior estimates, marking a significant milestone in planetary science. By scrutinizing over a decade’s worth of Hubble observations of Uranus’ aurorae, the researchers have refined the planet’s rotation period, creating a new foundational reference for ongoing investigations of planetary systems.

Captured by the Hubble Space Telescope in October 2022, the dynamic auroras of Uranus highlight the planet’s unique atmospheric phenomena. These observations, conducted by the Space Telescope Imaging Spectrograph (STIS), incorporate both visible and ultraviolet data. The technique employed allowed researchers to analyze more than ten years of Hubble’s auroral data, leading to a newly established rotation period that is crucial for future planetary explorations.

Determining a planet’s internal rotation is often challenging, especially for distant worlds like Uranus where direct measurements are impractical. The research team, led by Laurent Lamy from LIRA, Observatoire de Paris-PSL and LAM, Aix-Marseille University in France, devised a novel approach to monitor the rotational motion of Uranus through its auroral light displays. These lights are produced when energetic particles interact with the planet’s atmosphere near its magnetic poles. The results indicated that Uranus makes a complete rotation in 17 hours, 14 minutes, and 52 seconds—28 seconds longer than what was previously measured by NASA’s Voyager 2 during its flyby in 1986.

“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for the planetary science community but also resolves a long-standing issue: previous coordinate systems based on outdated rotation periods quickly became inaccurate, making it impossible to track Uranus’ magnetic poles over time,” says Lamy. “With this new longitude system, we can compare auroral observations spanning nearly 40 years and plan for future missions targeting Uranus.”

This important breakthrough hinges on Hubble’s extensive record of Uranus. Over an extended period, Hubble consistently recorded the planet’s ultraviolet auroral emissions, which enabled researchers to construct magnetic field models that accurately reflect the shifting positions of the magnetic poles over time.

“The continuous observations from Hubble were crucial,” adds Lamy. “Without this wealth of data, it would have been impossible to detect the periodic signal with this level of precision.”

In contrast to the auroral phenomena seen on Earth, Jupiter, or Saturn, the auroras of Uranus exhibit unique and erratic behaviors. This distinctiveness is attributable to the planet’s highly inclined magnetic field, which is greatly misaligned with its rotational axis. These recent findings not only enhance our understanding of Uranus’ magnetosphere but also deliver essential insights that will be pivotal for upcoming exploratory missions.

The implications of these results lay the groundwork for future research that will further unravel the mysteries of one of the Solar System’s most enigmatic planets. Thanks to its capability to conduct long-term monitoring of celestial bodies, the Hubble Space Telescope remains an invaluable asset for planetary science, facilitating a new era of exploration at Uranus.

The findings are documented based on observations garnered through Hubble’s programs, including GO #12601, 13012, 14036, 16313, and DDT #15380 (PI: L. Lamy). The research team’s paper is published in Nature Astronomy.

The Hubble Space Telescope, operational for over 30 years, continues to yield transformative discoveries, shaping our understanding of the universe. This mission exemplifies international collaboration between NASA and the European Space Agency (ESA). NASA’s Goddard Space Flight Center in Greenbelt, Maryland oversees the telescope and its mission operations, supported by Lockheed Martin Space in Denver. Scientific operations for Hubble are conducted by the Space Telescope Science Institute in Baltimore, an organization run by the Association of Universities for Research in Astronomy.

Source
science.nasa.gov