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19h ago

Webb Spots Tiny New Moon Around Uranus, Bringing Count to 29

IAU review will determine its official name once follow-up observations confirm the find.

Image
Astronomers using NASA’s James Webb Space Telescope discovered a new moon orbiting Uranus in images taken by Webb’s NIRCam (Near-Infrared Camera). This image shows the moon, designated S/2025 U1, as well as 13 of the 28 other known moons orbiting the planet. (The small moon Cordelia orbits just inside the outermost ring, but is not visible in these views due to glare from the rings.) Due to the drastic differences in brightness levels, the image is a composite of three different treatments of the data, allowing the viewer to see details in the planetary atmosphere, the surrounding rings, and the orbiting moons. The data was taken with NIRCam’s wide band F150W2 filter that transmits infrared wavelengths from about 1.0 to 2.4 microns. NASA, ESA, CSA, STScI, M. El Moutamid (SwRI), M. Hedman (University of Idaho)
image: ©forplayday | iStock

Overview

  • JWST’s NIRCam captured the object in ten 40‑minute near‑infrared exposures over nearly seven hours on February 2, 2025.
  • The provisional moon, designated S/2025 U1, is estimated to be about 10 kilometers wide and roughly 56,000 kilometers from Uranus’s center.
  • Its nearly circular orbit sits between the inner moons Ophelia and Bianca just beyond the planet’s narrow ring system.
  • The body is smaller and fainter than previously known inner moons, explaining why Voyager 2 and Hubble did not detect it.
  • With this detection and another candidate from 2023 pending confirmation, researchers report 29 identified Uranian moons and anticipate additional finds.