Uranus discovered to have a tiny new moon, so well hidden that Voyager 2 could not find it

DNVN - The James Webb Space Telescope (JWST) has just discovered a small moon orbiting Uranus that even Voyager 2 did not recognize during its historic flight in 1986.

James Webb has revealed Uranus’ smallest moon yet, a six-mile-wide planet hiding near its inner ring. The discovery brings the planet’s total number of known moons to 29 and suggests that Webb may uncover secrets that Voyager 2 never saw. Credit: NASA, ESA, CSA, STScI, M. El Moutamid (SwRI), M. Hedman (University of Idaho)

The newly discovered moon is just six miles wide, making it the ice giant’s 29th known moon. It lies near Uranus’ inner rings, adding a member to a family of bodies named after characters from the works of Shakespeare and Alexander Pope.

Discovery from James Webb

Scientists from the Southwest Research Institute (SwRI) led by Dr. Maryame El Moutamid used the JWST to observe Uranus on February 2, 2025. In a series of images taken with the Near Infrared Camera, the team discovered a faint, previously unknown object, which they tentatively named S/2025 U 1.

“As part of the JWST Guest Observer Program, we have discovered a previously unknown moon of the ice giant,” said Dr El Moutamid. “This is the smallest object ever discovered around Uranus, thanks to 10 long exposures from the camera system.”

If this moon has a similar albedo to its neighboring moons, it is estimated to be only about six miles (10 km) in diameter — much smaller than Voyager 2's detection threshold.

A new JWST survey led by SwRI has discovered S/2025 U 1 (approximate location marked in yellow), a small moon orbiting Uranus between Bianca and Ophelia. If it has an albedo similar to other nearby moons, the object would be about 10 km in diameter, making it by far the smallest moon in the Uranian system. The solid ellipses represent the rings, while the dotted lines show the orbits of many of the inner moons. Source: Public Domain

Uranus – the “sideways” planet

Uranus is the seventh planet from the Sun, and is notable for its unusual tilt, often referred to as the “sideways planet.” It is a blue-green ice giant with an atmosphere rich in hydrogen, helium, and methane.

Scientists believe that Uranus' larger moons are made up of roughly equal amounts of water ice and silicate rock. Of the 28 previously known moons, the five major ones - Titania, Oberon, Umbriel, Ariel and Miranda - were discovered between 1787 and 1948.

Memories of Voyager 2's historic flight

Voyager 2 is the only spacecraft to visit Uranus. On January 24, 1986, it approached the planet at a distance of 80,000 km (50,000 miles) above the clouds above, capturing thousands of images. It was this flyby that led to the discovery of the ring system and numerous small moons, 10 of which were later officially named.

The Southwest Research Institute led a survey using the James Webb Space Telescope (JWST) that discovered a previously unknown moon (circled) orbiting Uranus between the moons Bianca and Ophelia. This image shows the tiny moon, dubbed S/2025 U1, as well as 13 of the 28 other known moons orbiting the planet. (The small moon Cordelia, which orbits just inside the outermost ring, is not visible here due to the glare from the rings.) Because of the large difference in brightness, this image is a composite of three different data treatments, revealing details of the planet's atmosphere, surrounding rings, and orbiting moons. Credit: NASA, ESA, CSA, STScI, M. El Moutamid (SwRI), M. Hedman (University of Idaho)

Orbit and position of the “new moon”

The newly discovered moon lies on the edge of Uranus’ inner ring, about 35,000 miles (56,250 km) from the planet’s center, on the equatorial plane. It orbits between two other small moons: Ophelia, which is about 13 miles (43 km) in diameter, and Bianca, an elongated body measuring 40 by 29 miles (64 by 46 km).

“With so many of Uranus’ moons named after Shakespearean characters, our team now has to learn more about the culture to find an appropriate name for this new discovery,” El Moutamid shared.

La Khe (According to SciTech Daily)

Source: https://doanhnghiepvn.vn/cong-nghe/phat-hien-sao-thien-vuong-co-trang-non-sieu-nho-an-nap-ky-nen-tau-voyager-2-khong-tim-ra/20250827042628900