A team of scientists from the Southwest Research Institute in Boulder, Colorado, have discovered a new moon orbiting the planet Uranus in images taken by the James Webb Space Telescope, according to a press release issued by NASA on 19 August 2025. The team, headed by lead scientist Maryame El Moutamid, discovered the moon in a series of 40 second exposures of the planet taken on 2 February 2025.
The new moon has been given the provisional designation S/2025 U1 (indicating the first Satellite discovered orbiting Uranus in 2025). If the discovery is confirmed, it will be formally given a name, which in the case of moons of Uranus is chosen from characters in the plays of William Shakespear or Alexander Pope.
S/2025 U1 has an estimated diameter of 8-10 km, and orbits 56 250 km above the centre of Uranus (as a gas giant, Uranus does not have a 'surface'), between the moons Ophelia and Bianca. This makes it extremely faint, which combined with its proximity to the planet, appears to have hidden it from previous observations by Voyager 2 and the Hubble Space Telescope.
S/2025 U1 is the first moon of Uranus discovered in two years, with the most recent discovery previously being S/2023 U1 (which has not yet been confirmed, and therefore still has a provisional designation) discovered in 2023 by American Astronomer Scott Sheppard using the 6.5-meter Magellan–Baade Telescope at Las Campanas Observatory in Chile. Prior to this, the moons Cupid, Mab, and Margaret were discovered in 2003 using the Hubble Space Telescope, while Francisco was discovered in the same year using the 4.0-meter Víctor M. Blanco Telescope at Cerro Tololo Observatory, again in Chile. In 2001 the moons Trinculo and Ferdinand were also discovered using the 4.0-meter Víctor M. Blanco Telescope. In 1999 the moon Perdita was discovered in photographs made by the Voyager 2 spacecraft during its flyby of Uranus in 1986. Also in 1999, the moons Stephano, Prospero, and Setebos were discovered using the Canada-France-Hawaii Telescope on Mauna Kea. In 1997 the moons Caliban and Sycorax were discovered using the 200-inch Hale Telescope at the Palomar Observatory in California. In 1986 the moons Cordelia, Ophelia, Bianca, Cressida, Desdemona, Juliet, Portia, Rosalind, and Belinda were discovered by the Voyager 2 Spacecraft during its flyby of Uranus, with Puck discovered the previous year as the spacecraft approached the planet.
Prior to this, the last moon of Uranus discovered had been Miranda, discovered in 1948 by Gerard Kuiper (after whom the Kuiper Belt is named), then working at McDonald Observatory in Texas. Almost a century before this the English astronomer William Lassell discovered the moons Ariel and Umbriel, using a 24 inch telescope he built himself and operated from a suburb of Liverpool. This first two moons of Uranus to be discovered (and its largest moons), Titania and Oberon, were discovered on 11 January 1787 by William Herschel, six years after he discovered the planet itself.
S/2025 U1 is the smallest moon of Uranus yet discovered, and appears to be the fourteenth member of a group of small moons orbiting inside the major moons of Uranus (Titania, Oberon, Arial, Umbriel, and Miranda) but outside the planets rings (the remaining moons are small bodies with eccentric and often retrograde orbits outside the major moons, which may be captured comets or asteroids). These small moons all have very circular orbits, which suggests that they formed in their current locations, hinting at a complex relationship with the particles of the rings.
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