NASA has announced the discovery of a previously unknown moon orbiting the planet Uranus, now designated S/2025 U1. The find was made possible by the James Webb Space Telescope (JWST), which captured images of the small moon on February 2, 2025. This discovery brings the total count of Uranus' confirmed moons to 29.
The research team, led by Miriam Metmaday from the Southwest Research Institute (SwRI) in Boulder, Colorado, utilized ten 40-minute exposures from JWST's Near-Infrared Camera (NIRCam) to detect the faint object. The newly identified moon is estimated to be approximately 10 kilometers (about 6 miles) in diameter, a size that likely contributed to its elusiveness for earlier missions, including the Voyager 2 probe during its 1986 flyby.
S/2025 U1 orbits Uranus at a distance of roughly 56,000 kilometers (approximately 35,000 miles) from the planet's center. It is situated within the planet's inner moon system, specifically between the orbital paths of Ophelia and Bianca. The moon's nearly circular orbit suggests it may have formed in its current vicinity. This discovery is particularly significant as Uranus is known for its numerous small inner moons, which play a complex role in shaping the planet's ring system, hinting at a dynamic history for Uranus's moons and rings.
Matthew Tiscareno of the SETI Institute, a member of the discovery team, noted that S/2025 U1 is fainter than previously known inner moons, suggesting that further complexities within the Uranian system are likely yet to be uncovered. Historically, Uranus's moons are named after characters from the literary works of William Shakespeare and Alexander Pope. The International Astronomical Union (IAU) will be responsible for assigning a formal name to S/2025 U1, continuing this tradition.