A team of astronomers using NASA’s European Space Agency (ESA) Hubble Space Telescope has made precise measurements of Uranus’ rotation rate, achieving accuracy 1000 times greater than previous estimates. By analyzing more than a decade of Hubble observations of the planet’s aurorae, researchers have refined Uranus’ rotation period and established a crucial reference point for future planetary research.
Determining a planet’s interior rotation rate is challenging, particularly for Uranus, where direct measurements are not possible. To overcome this, scientists developed an innovative method to track the rotational motion of Uranus’ aurorae – spectacular light displays generated in the upper atmosphere by energetic particles near the magnetic poles. This technique revealed that Uranus completes a full rotation in 17 hours, 14 minutes, and 52 seconds.
The new measurement is not only essential for planetary science but also resolves a long-standing issue with outdated rotation periods, which made it difficult to track Uranus’ magnetic poles over time. With this new reference point, astronomers can now compare auroral observations spanning nearly 40 years and plan for the upcoming Uranus mission.
Hubble’s long-term monitoring of Uranus was crucial in achieving this breakthrough. Over a decade, Hubble regularly observed its ultraviolet auroral emissions, enabling researchers to track the position of the magnetic poles with magnetic field models.
The unique behavior of Uranus’ aurorae is due to the planet’s highly tilted magnetic field, which is significantly offset from its rotational axis. The findings not only help astronomers understand Uranus’ magnetosphere but also provide vital information for future missions.
These results are based on observations acquired with Hubble programmes GO #12601, 13012, 14036, 16313 and DDT #15380 (PI: L. Lamy). The team’s paper has been published today in Nature.
Source: https://esahubble.org/news/heic2503