With the help of the space telescope James Webb, an international team has identified a tiny moon in Uranus, a discovery that extends the census of the planet to 29 satellites known and puts the distant blue-green world back in the spotlight of the scientific community.
The detection of this small body, about 10 kilometers in diameter, strengthens Webb's ability to study the outer solar system and provides clues about the complex environment of rings and inner moons that accompanies Uranus.
The find
La new moon was identified during a session of the February 2th 2025, when the near infrared camera NIR Cam I take ten exhibitions long-lasting, each about 40 minutes.
According to the person responsible for the analysis, Maryame El Moutamid, from the Southwest Research Institute In Boulder, Colorado, the object appears as an extremely faint point in the images, overlooked by Voyager 2 in its historic 1986 flyby.
Data were obtained within the framework of the program General Observer del Webb, which opens the telescope to proposals from the community, allowing for research remote regions of the Solar System with unprecedented sensitivity.
Orbit, size and location
Estimates point to a diameter of about 10 km, calculated assuming a reflectivity similar to that of other minor satellites of Uranus.
The object describes a almost circular orbit a 56.000 kilometers from the center of the planet, in the equatorial plane, located between the trajectories of Ofelia and Bianca and just beyond the outer edge of the main ring system.
With this finding it is incorporated as the fourteenth member of the intricate set of small inner moons, inside the big five: Miranda, Ariel, Umbriel, Titania and Oberon.
In the same vicinity also orbit satellites such as Mab and Cordelia, whose interactions with the rings show a dynamic and chaotic evolution of the Uranian system.
Why it went unnoticed
Su low brightness and tiny size They explain why it was not captured by previous instruments, including the hubble telescope and the probe Voyager 2, despite the latter's flyover almost four decades.
The combination of the high angular resolution and the Webb's near-infrared sensitivity is what has made it possible to distinguish this weak point from the background, something beyond the reach of previous observations.
In fact, the last time a satellite was added to the Uranian inventory through telescopic observations was in 2003, which underlines the technological leap of the modern astronomy.
For several researchers, including Matthew Tiscareno from the SETI Institute, the finding suggests that There could be more tiny moons in the surrounding area, waiting to be detected with additional observation campaigns.
Provisional name and next steps
The body is designated for now S/2025 U1, a provisional label until the International Astronomical Union confirm your status and assign a formal name.
Following tradition, the moons of Uranus They adopt names of characters from William Shakespeare y Alexander Pope; any proposal must respect that convention once it is validated the orbits with more data.
In parallel, the team plans new follow-up observations to fine-tune the orbital period, albedo and shape of the satellite, parameters that will help understand its origin and long-term stability.
With the addition of this small world to the Uranian family, the count rises to 29 known moons and the role of the James Webb as a key tool to reveal elusive details of the system of rings and satellites of Uranus, from its orbit at 56.000 km to its status as a possible stable member of the inner swarm.
