New Uranus moon S2025 U1 discovered by JWST, bringing total to 29

A newly identified moon orbiting Uranus has brought the planet’s known satellite family to 29, underscoring the ongoing gaps in our view of the ice giant’s intricate system. The small moon, provisionally designated S2025 U1, is about six miles (10 kilometers) across and sits roughly 35,000 miles (56,000 kilometers) from Uranus’s center, between the orbits of Ophelia and Bianca. The discovery was made on February 2, 2025, through a series of ten 40-minute exposures captured with the James Webb Space Telescope’s Near-Infrared Camera, by a team led by the Southwest Research Institute in Colorado.

The newly found moon is part of Uranus’s dense family of inner moons that orbit well inside the planet’s largest satellites. It is the 14th such inner moon identified, a group that lies inward of Miranda, Ariel, Umbriel, Titania, and Oberon and interact closely with Uranus’s ring system. The moon’s nearly circular orbit suggests it formed near its present location, a pattern that researchers say adds to the impression of a dynamically rich and somewhat chaotic history around Uranus. The moon’s small size and faint reflectivity likely explain why it eluded Voyager 2 during its 1986 flyby,...