NASA scientists using the James Webb Space Telescope have identified a previously unknown moon orbiting Uranus, raising the planet’s tally of confirmed satellites to 29. The object, provisionally designated S/2025 U1, was detected in a series of ten 40-minute exposures captured by Webb’s Near-Infrared Camera on 2 February 2025 under a programme led by the Southwest Research Institute. At an estimated six miles (10 kilometres) across, S/2025 U1 is smaller and fainter than any inner moon previously catalogued around the ice giant—dimensions that kept it hidden from Voyager 2 during its 1986 fly-by and from Earth-based observatories. The moon follows a nearly circular path about 35,000 miles (56,000 kilometres) from Uranus’ centre, slotting between the orbits of the small satellites Ophelia and Bianca. Researchers say the discovery highlights the complexity of Uranus’ inner system, where 14 compact moons interact with 13 dark rings. “No other planet has as many small inner moons,” said SwRI scientist Maryame El Moutamid, adding that Webb’s infrared sensitivity is likely to reveal further details—and possibly additional bodies—within the chaotic region. The International Astronomical Union will assign an official name to S/2025 U1 after confirming its orbital parameters.