James Webb Telescope Discovers Tiny New Moon Orbiting Uranus

A tiny new moon orbiting icy Uranus, the seventh planet from the sun, has been discovered by a group of scientists at the Southwest Research Institute (SwRI) in Colorado using NASA's James Webb Space Telescope. The moon, known as S/2025 U1, is just 6 miles (10 kilometers) or so in diameter, which made it invisible to NASA's Voyager 2 probe during its 1986 flyby of the planet, as well as rendering it undetectable by other telescopes. Its discovery brings the total number of known Uranian moons to 29.

About the discovery

According to Maryame El Moutamid, a lead scientist in SwRI's Solar System Science and Exploration Division based in Boulder, Colorado, a series of 10 40-minute long-exposure images captured by the Near-Infrared Camera (NIRCam) revealed the presence of this new moon. The moon is only about 6 miles (10 kilometers) across — extremely small, just a fraction of the size of Earth's moon. Its tiny size is why earlier spacecraft and telescopes never spotted it.

The new moon is the 14th member of the intricate system of small moons orbiting inward of the largest moons Miranda, Ariel, Umbriel, Titania, and Oberon. It orbits roughly 35,000 miles (56,000 kilometers) from Uranus's center on a nearly circular path, suggesting it formed near its present location among Uranus's other small inner moons.

Significance

Uranus now has 29 known moons — one of the most crowded collections of moons around any planet. Many of these satellites are tiny and orbit very close to the planet. Finding S/2025 U1 suggests there could be more hidden moons or ring fragments still awaiting discovery, highlighting how much remains to be learned about Uranus. When Voyager 2 flew past Uranus in 1986, it found only five moons.
Webb has since spotted a much smaller moon that Voyager missed. Webb is revealing surprises around familiar planets. By studying these tiny moons and their rings, scientists hope to better understand how the Uranian system formed and evolved. Each new find is a piece of the puzzle, helping researchers unravel the story of this distant, icy world.

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