S/2025 U 1

S/2025 U 1 is one of the smallest known moons of Uranus,^[2] with an estimated diameter between 8 and 10 km (5 and 6 mi).^[3] It was reported on 19 August 2025 by a team of astronomers led by Maryame El Moutamid,^[a] who found the moon in James Webb Space Telescope NIRCam images taken on 2 February 2025.^[1][b] It orbits about 56,250 km (34,950 mi) from the center of Uranus (between the orbits of Ophelia and Bianca) with an orbital period of 9.6 hours (0.402 days).^[1] Like the other inner moons of Uranus, it follows a nearly circular orbit along Uranus's equatorial plane.^[1] Due to its small size, it appears extremely faint with a near-infrared (H-band) apparent magnitude of 25.5—too faint to be seen by the Hubble Space Telescope and the Voyager 2 spacecraft.^[1]

S/2025 U 1

Discovery image of S/2025 U 1 (circled) by the James 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[1]
Semi-major axis	56250±250 km
Eccentricity	≈ 0
Orbital period (sidereal)	0.402 d (9.6 h)
Inclination	≈ 0°
Satellite of	Uranus
Physical characteristics
Mean diameter	8–10 km[1]
Albedo	0.05–0.10 (assumed)[1]

Name

S/2025 U 1 is the provisional designation of this unnamed moon.^[2] By convention, the moons of Uranus are named after characters from the plays of William Shakespeare and Alexander Pope.^[3] A proper name will be given once it is approved by the International Astronomical Union.^[3][2] Co-discoverer Mark R. Showalter has stated in a 2025 NewScientist article that "there have been discussions [of a name for S/2025 U 1] but no shortlist as yet."^[2]

Orbit

JWST timelapse of S/2025 U 1 (circled) orbiting Uranus, along with Miranda (upper left) and the rest of Uranus's inner moons

S/2025 U 1 is the 14th known member of Uranus's inner moons, which are small moons that orbit interior to the planet's five largest moons (Miranda, Ariel, Umbriel, Titania, and Oberon).^[3] S/2025 U 1 follows a nearly circular orbit around Uranus's equatorial plane, at a distance of 56,250 km (34,950 mi) from the planet's center with an orbital period of 9.6 hours (0.402 days).^[1] S/2025 U 1 is located outside the edge of Uranus's inner ring system, between the orbits of Ophelia and Bianca.^[2] The nearly circular orbit of S/2025 U 1 suggests that it formed near its current location, according to discoverer Maryame El Moutamid.^[3]

Notes

1. The full team of researchers involved in the discovery of this moon includes: Maryame El Moutamid, Matthew M. Hedman, Mark R. Showalter, Matthew Tiscareno, Imke de Pater, Jack J. Lissauer, and Damya Souami.^[1]
2. The NIRCam discovery observations consisted of ten consecutive near-infrared images, each with 40-minute-long exposure times.^[3]