James Webb Telescope Unveils Tiny New Moon Orbiting Uranus, Expanding Planet’s Satellite Count to 29

Astronomers discovered a new moon orbiting Uranus, thanks to the superpower vision of the James Webb Space Telescope (JWST). S/2025 U1 is tiny, measuring just 6 miles (10 kilometers) across—the diameter at which you could walk around it in under two hours.

The moon was first seen on Feb. 2, 2025, as one of a series of ten 40-minute long-exposure photographs captured by JWST's Near-Infrared Camera (NIRCam). It circles around Uranus at a distance of about 35,000 miles (56,000 kilometers) between the orbits of moons Ophelia and Bianca. The discovery brings the number of known Uranian moons to 29.

Its faintness and proximity to Uranus likely rendered it invisible to previous missions, including the 1986 flyby of Voyager 2. Scientists interpret the moon's nearly circular orbit as a sign that it probably formed where it is located, and that informs scientists about the extremely dynamic early evolution of the planet.

Uranus is unique in having a dense inner system of small moons and dark, mysterious rings. The interaction between these features implies an active history that marks the dividing line between ring systems and moon systems. Scientists note that there are likely other concealed moons yet to be discovered.

This finding not only deepens our knowledge about Uranus but also showcases JWST's unmatched capability to detect faint, far-off objects in our solar system. The moon remains nameless for the moment, to be determined by the International Astronomical Union.