James Webb Telescope Finds Hidden Moon Orbiting Uranus

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NASA's James Webb Space Telescope has uncovered a small moon quietly circling Uranus, a world already known for its unusual tilt, faint rings, and puzzling family of satellites. The discovery, announced by researchers at the Southwest Research Institute (SwRI), raises the tally of Uranus' moons to 29.

The moon, temporarily called S/2025 U1, was spotted on February 2, 2025, in a set of ten long-exposure images taken with Webb's Near-Infrared Camera. Each image required forty minutes of exposure to capture enough light from the distant planet and its surroundings.

"This object was spotted in a series of 10 40-minute long-exposure images captured by the Near-Infrared Camera," said Maryame El Moutamid of SwRI's Solar System Science and Exploration Division in Boulder, Colorado. "It's a small moon but a significant discovery, which is something that even NASA's Voyager 2 spacecraft didn't see during its flyby nearly 40 years ago."

Voyager 2, the only spacecraft to visit Uranus up close, passed by on January 24, 1986. While it transformed scientists' understanding of the icy giant, its instruments were not sensitive enough to detect such a tiny object.

At only six miles (10 kilometers) in diameter, the new moon is tiny compared with Uranus' five largest satellites— Miranda , Ariel, Umbriel, Titania, and Oberon. Its size and low brightness made it virtually invisible to earlier telescopes. Researchers estimate that the small world reflects light in a way similar to Uranus' other inner moons, which explains why it has been hiding within the planet's crowded ring system for so long.

Located about 35,000 miles (56,000 kilometers) from Uranus' center, the moon sits neatly between the orbits of Ophelia and Bianca. Its nearly circular path suggests it may have formed right where it is today, rather than being captured later. This places it among the 14 inner moons that orbit closer to Uranus than the larger and more distant satellites.