SwRI-led Webb Telescope survey discovers new moon orbiting Uranus

SAN ANTONIO — August 19, 2025 — Southwest Research Institute led a James Webb Space Telescope (JWST) survey, discovering a previously unknown tiny moon orbiting Uranus. A team led by SwRI’s Dr. Maryame El Moutamid discovered the small object in a series of images taken on Feb. 2, 2025, bringing Uranus’ total moon count to 29.

“As part of JWST’s guest observer program, we found a previously unknown satellite of the ice giant, which has been provisionally designated S/2025 U 1,” said El Moutamid, a lead scientist in SwRI’s Solar System Science and Exploration Division in Boulder, Colorado. “This object, by far the smallest object discovered to date, was detected in a series of 10 long exposures obtained by the Near-Infrared Camera.”

Located in the outer solar system, Uranus is the seventh planet from the Sun. Known as “the sideways planet” for its extreme axial tilt, the cyan-colored ice giant has a deep atmosphere composed of hydrogen, helium and methane. Scientists think Uranus' larger moons are roughly equal parts water ice and silicate rock.

“Assuming that the new moon has an albedo comparable to other nearby satellites, this object is probably around six miles (10 km) in diameter,” El Moutamid said. “It is well below the detection threshold for the Voyager 2 cameras.”

Voyager 2 is the only spacecraft to visit Uranus so far, coming within 50,000 miles of its cloud tops on Jan. 24, 1986. The spacecraft collected thousands of images, discovering rings and small satellites, including 10 of its named moons.

Uranus’ 28 moons include five major moons — Titania, Oberon, Umbriel, Ariel and Miranda — discovered between 1787 and 1948. Known as “the literary moons,” Uranus satellites are named for characters in Shakespeare and the works of Alexander Pope.

The new moon is at the edge of Uranus’ inner rings. It is located about 35,000 miles (56,250 km) from its center in the planet's equatorial plane, between the orbits of Ophelia and Bianca. Ophelia is about 13 miles (43 km) in diameter, while Bianca is an elongated object around 40 by 29 miles (64 by 46 km) in dimension.

“With so many of Uranus’ moons named for Shakespearean characters, our team is getting a lot of culture trying to figure out what to name our new discovery,” El Moutamid said.

For more information, visit https://www.swri.org/markets/earth-space/space-research-technology/space-science/planetary-science .