Voyager 2 discovered ten moons when it flew past Uranus in 1986. Nearly 40 years later, James Webb found one it missed: Uranus's 29th known moon, a tiny world only about 10 kilometres wide hiding amon
The James Webb Space Telescope has identified a new, tiny moon orbiting Uranus, designated S/2025 U1, which was previously missed by Voyager 2 in 1986. This discovery highlights the advancements in infrared sensitivity and observational techniques in modern astronomy.
Why it matters
It expands our understanding of the Uranian system and demonstrates the superior capabilities of next-generation space observatories.
Webb's ten long infrared exposures found S/2025 U1 between Ophelia and Bianca, extending a moon census begun by Voyager 2 while exposing how much remains unresolved around Uranus.
By Lachlan Brown · Edited by Lachlan Brown
When Voyager 2 crossed the Uranian system on 24 January 1986, its cameras found ten moons that had never been seen before. The single encounter more than doubled the known population of small satellites around the planet and established a family of dark bodies packed around its narrow rings.
On 2 February 2025, the James Webb Space Telescope watched Uranus for roughly six hours and recorded a faint moving point between the orbits of Ophelia and Bianca. The object is probably only about 10 kilometres across. Under the provisional designation S/2025 U1, it raised the current total to 29 known Uranian moons.
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