S/2025 U 1

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S/2025 U 1
Uranus new moon 2025 JWST.png
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 date2 February 2025
(date of discovery images) [1]
Orbital characteristics [1]
56250±250 km
Eccentricity ≈ 0
0.402 d (9.6 h)
Inclination ≈ 0°
Satellite of Uranus
Physical characteristics
8–10 km (5–6 mi) [1] [2]
Albedo 0.05–0.10 (assumed) [1]
25.5 (H-band)

    S/2025 U 1 is a small moon of Uranus, [3] with an estimated diameter between 8 and 10 kilometres (5 and 6 miles). [2] It was the 29th moon identified in the Uranus system. The discovery was announced in 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]

    Contents

    The moon 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]

    Name

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

    Orbit

    JWST timelapse of S/2025 U 1 (circled) orbiting Uranus, along with Miranda (upper left) and the rest of Uranus's inner moons S2025 U1 discovery video.gif
    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). [2] 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. [3] The nearly circular orbit of S/2025 U 1 suggests that it formed near its current location, according to El Moutamid. [2]

    Notes

    1. 1 2 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. [2]

    References

    1. 1 2 3 4 5 6 7 8 9 10 11 Green, Daniel W. E. (19 August 2025). "CBET 5593: S/2025 U 1". Central Bureau Electronic Telegram. Central Bureau for Astronomical Telegrams. Retrieved 19 August 2025.
    2. 1 2 3 4 5 6 7 El Moutamid, Maryame (19 August 2025). "New Moon Discovered Orbiting Uranus Using NASA's Webb Telescope". NASA. Retrieved 19 August 2025.
    3. 1 2 3 4 5 Sparkes, Matthew (19 August 2025). "New moon discovered orbiting Uranus is its smallest one". NewScientist. Archived from the original on 19 August 2025. Retrieved 19 August 2025.
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