Webb Discovers Uranus’s 29th Moon, a Tiny 10-km World Voyager 2 Missed

The James Webb Space Telescope found a new Uranian moon, S/2025 U1, about 10 kilometers across, between Ophelia and Bianca, bringing Uranus’s known moons to 29. Voyager 2’s 1986 flyby had already discovered 10 moons (with Perdita later identified in archival data), but its brief, changing view and instrumental limits mean it could miss small objects like this. Webb’s six-hour infrared observations confirmed the moon’s movement, and its proximity to rings and inner moons offers new data for modeling Uranus’s system. The discovery highlights how different observing methods reveal unseen bodies and how future missions could further illuminate the Uranian system.