Newly Discovered Moon Reveals Uranus Has the Smallest Orbit of Its Kind

A recently discovered, faint moon orbits Uranus, bringing its total count to 29. Several of the other moons of this gas giant bear names from the works of William Shakespeare, and there are discussions among scientists about which character will inspire the new moon’s name.

The moon was uncovered by a team led by Maryame El Moutamid from the Southwest Research Institute in Colorado, utilizing 10 long-exposure infrared images captured by NASA’s James Webb Space Telescope (JWST) on February 2 this year.

For now, the moon is temporarily designated as S/2025 U 1. However, it is likely to receive a name aligned with the tradition of naming Uranus’ moons after characters from Shakespeare’s plays, a convention established since the discovery of Titania and Oberon, the planet’s first two moons, in 1787.

All proposed names for newly discovered moons must receive approval from the International Astronomical Union (IAU), the authoritative body responsible for assigning names and designations to celestial objects. Mark Showalter from the Seti Institute, who is part of the research team and an avid theater enthusiast, mentioned that while there hasn’t been any discussion on candidates yet, it’s certainly an intriguing proposition.

Showalter described the challenge of detecting such a small, dim moon, comparing it to “trying to see a fly while staring directly at the headlights of a car.” He expressed admiration for the James Webb telescope’s sensitivity, which far exceeds that of any telescope that has come before it.

There is optimism for more moons to be discovered around Uranus, as Showalter remarked, “We certainly haven’t completed our observations.” He believes it’s reasonable to propose that additional satellites exist, particularly those that may influence the ring system.

El Moutamid pointed out that the clarity of Uranus’ rings suggests there could be more undiscovered moons associated with their formation. “Perhaps there are more waiting to be identified,” she added. Some could be uncovered by the JWST, while others may be detected by a proposed Uranus orbiter and probe mission targeted for 2044. “There likely are many very small moons that remain invisible due to the limitations of current observational methods,” she said.

The S/2025 U1 is estimated to measure around 10 km in diameter, rendering it too small to be captured by cameras on the Voyager 2 probe, which launched in 1977 and passed Uranus in 1986, coming within around 81,500 kilometers. To date, it remains the closest encounter with Uranus by any spacecraft from Earth.

The new moon resides at the inner edge of Uranus’ rings, situated approximately 56,250 kilometers from the center of the planet’s equatorial plane, fitting between the orbits of the moons Ophelia and Bianca.

NASA oversees the JWST’s “General Observer” program, which allows researchers worldwide to propose observation targets that require one of the telescope’s advanced sensors. El Moutamid dedicated time to studying Uranus’ rings using the JWST’s Nircam Instrument (a high-resolution infrared sensor), which ultimately led to the discovery of this new moon.