S/2025 U 1

Discovery image of S/2025 U 1 (circled) by theJames Webb Space Telescope on 2 February 2025
Discovery[1]
Discovered by	Maryame El Moutamid et al.[a]
Discovery site	James Webb Space Telescope
Discovery date	2 February 2025 (date of discovery images)[1]
Orbital characteristics[2]
Epoch 1 January 2025TDB
Semi-major axis	57844 km
Eccentricity	0.039
Orbital period (sidereal)	0.4021 d (9.65 h)
Mean anomaly	275.6°
Inclination	4.0° (wrt localLaplace plane[b])
Longitude of ascending node	70.8°
Argument of perihelion	313.9°
Satellite of	Uranus
Physical characteristics
Mean diameter	8–10 km (5–6 mi)[1][3]
Meandensity	0.5–1.2 g/cm3[4]
Albedo	0.05–0.10 (assumed)[1]
Apparent magnitude	25.5 (H-band)

S/2025 U 1 is a smallmoon of Uranus, with an estimated diameter between 8 and 10 kilometres (5 and 6 miles).^[3] It was the 29th moon identified in theUranian system. The discovery was announced in August 2025 by a team of astronomers led byMaryame El Moutamid,^[a] who found the moon inJames Webb Space TelescopeNIRCam images taken on 2 February 2025.^[1][c]

The moon orbits about 57,844 km (35,943 mi) from the center of Uranus (between the orbits ofOphelia andBianca) with anorbital period of 9.6 hours (0.402 days).^[2] Like the otherinner moons of Uranus, it follows a nearlycircular orbit along Uranus's equatorial plane.^[1] Due to its small size, it appears extremely faint with anear-infrared (H-band)apparent magnitude of 25.5—too faint to be seen by theHubble Space Telescope and theVoyager 2spacecraft.^[1]

S/2025 U 1 is theprovisional designation of this unnamed moon.^[5] By convention, the moons of Uranus are named after characters from the plays ofWilliam Shakespeare andAlexander Pope.^[3] A proper name will be given once it is approved by theInternational Astronomical Union.^[3][5] Co-discovererMark R. Showalter has stated in a 2025New Scientist article that "there have been discussions [of a name for S/2025 U 1] but no shortlist as yet."^[5]

S/2025 U 1 is the 14th known member of Uranus'sinner moons, which are small moons that orbit interior to the planet's five largest moons (Miranda,Ariel,Umbriel,Titania, andOberon).^[3] S/2025 U 1 follows a nearlycircular orbit around Uranus's equatorial plane, at a distance of 57,844 km (35,943 mi) from the planet's center with anorbital period of 9.6 hours (0.402 days).^[2] S/2025 U 1 is located outside the edge of Uranus's innerring system, between the orbits ofOphelia andBianca.^[5] The nearly circular orbit of S/2025 U 1 suggests that it formed near its current location, according to El Moutamid.^[3]

• James Webb Space Telescope (JWST) (19 August 2025)."New Moon Discovered Orbiting Uranus Using NASA's Webb Telescope (video)".YouTube.
• El Moutamid, Maryame; et al. (10 September 2025).New JWST Discoveries on the Uranian System.EPSC-DPS Joint Meeting 2025. Vol. 18. Finlandia Hall, Helsinki, Finland.doi:10.5194/epsc-dps2025-421. EPSC-DPS2025-421.
• El Moutamid, Maryame; et al. (12 December 2024)."JWST Proposal 6379 – Structure and Dynamics of The Rings and Inner Moons of Uranus". Space Telescope Science Institute. Cycle 3.

• Moons of Uranus
• Moons with a prograde orbit
• Astronomical objects discovered in 2025
• Discoveries by the James Webb Space Telescope

• Articles with short description
• Short description is different from Wikidata
• Use dmy dates from August 2025