For nearly four decades, a tiny secret remained hidden in the icy shadows of Uranus. Despite the historic flyby of NASA’s Voyager 2 in 1986, a small, elusive world managed to escape detection—until now. Thanks to the piercing infrared gaze of the James Webb Space Telescope (JWST), astronomers have officially announced the discovery of a new moon, provisionally named S/2025 U1.
A Micro-World Hidden in Plain Sight.
Measuring just 10 kilometers (6 miles) in diameter—roughly the size of a small city—S/2025 U1 is the smallest moon ever discovered orbiting the “Sideways Planet.” Its discovery brings Uranus’s total moon count to 29, further complicating the intricate celestial dance of the ice giant’s satellite system.
The moon was first spotted in data captured on February 2, 2025, by a team led by Dr.
Maryame El Moutamid of the Southwest Research Institute (SwRI). It took a series of ten 40-minute long-exposure images using Webb’s Near-Infrared Camera (NIRCam) to confirm that the faint speck of light was indeed an orbiting body and not mere cosmic background noise.
Where is S/2025 U1?
The new moon occupies a busy neighborhood. It orbits approximately 56,000 kilometers (35,000 miles) from Uranus’s center, tucked neatly between the orbits of two other inner moons: Ophelia and Bianca.
Scientists believe S/2025 U1 is part of the “inner moon” group, which are thought to be closely related to the planet’s ring system. Its nearly circular orbit suggests it formed in its current location rather than being captured by Uranus’s gravity later in history.
The Shakespearean Tradition.
While it currently carries the technical designation S/2025 U1, the moon won’t stay unnamed for long. Following a long-standing tradition, the International Astronomical Union (IAU) will eventually grant it a permanent name derived from the works of William Shakespeare or Alexander Pope. It will soon join the ranks of Titania, Oberon, and Puck in the legendary Uranian cast.
Why This Discovery Matters.
- Ring Stability: Tiny “shepherd moons” like this one often use their gravity to keep Uranus’s narrow rings from spreading out.
- System Evolution: The presence of such small inner moons provides clues about the collision-heavy history of the Uranian system.
As we look toward future missions to the outer solar system, S/2025 U1 serves as a reminder that even “well-mapped” planets still hold surprises for those with the right tools to see them.