According to NASA, astronomers using the powerful eyes of James Webb’s space telescope found a previously unknown moon that was circling around Uranus. This discovery increases the number of months known to orbit the ice giant to 29.
The moon was revealed through a series of 40-minute long exposure images taken by Webb’s near-infrared camera on February 2nd.
“It’s a small moon, but it’s a serious discovery. This is something we didn’t even see on NASA’s Voyager 2 spacecraft on a flyby nearly 40 years ago,” said Mary El Mutamide, the chief scientist in the Department of Solar System Science and Exploration in Boulder, Colorado.
El Moutamid is the lead researcher of the Webb program dedicated to analyzing the structure and dynamics of the hidden ring and the inner moon of Uranus.
The tiny-sized glow of the Uranus ring and the moon, about six miles (10 kilometers) in diameter, could have blurred it from the scenery of Voyager 2, the only mission to play the flybee of Uranus and Neptune, as well as the only mission to play a Hubble-like telescope that observed planets outside the solar system.
According to El Moutamid, some of the materials that make up the rings of the moon and Uranus may have a common origin.
The moon, temporarily named the S/2025 U1, can reveal how the Uranus ring is shaped, whether it be gravity or an ancient event, and provides a window into the structure, stability and history of the enigmatic ring, she said.
“This discovery raises questions about how it interacts with the ring with the small moon that remains hidden around Uranus,” Elmutamide said.
The discovery of the moon around planets in our solar system is not a very common event, but it occurs from time periods around giant planets such as Jupiter, Saturn, Uranus, and Neptune.
“There are many moons on these planets, some are so small and faint that we are still discovering,” Elmutamide said.
The newly discovered month is 14th In a small lunar system orbiting Uranus, all of which are closer to planets than the largest moons of Miranda, Ariel, Ambriel, Titania and Oberon.
“It is located about 35,000 miles (56,000 km) from the center of Uranus and orbits the planet’s equatorial plane between the orbit of Ophelia (just outside the Uranus’ main ring system) and Bianca,” Elmutamide said, referring to the two other small moons surrounding the planet. “Its almost circular trajectory suggests that it may have formed near its current location.”
Finding the moon was not easy, according to El Moutamid. The high resolution and sensitivity of Webb’s near-infrared cameras were perfectly suited to find faintly distant objects, she said.
Webb’s ability to capture infrared rays that are invisible to the human eye gave us a glimpse into the rings and moon, the atmosphere and weather of Uranus during previous observations.
“The detection highlights both the dynamic complexity of Uranus’ systems and the keen eye of modern astronomy.”
So far, all of Uranus’ moons have been named after the characters from the works of William Shakespeare and Alexander Pope.
Previously unknown moons still lack a literary name. The International Astronomical Union, which assigns official names to objects in the heavenly world, must approve them.
“They’re the best,” said Scott Shepherd, an astronomer at the Carnegie Science Facility in Washington, DC. Shepherd was not involved in the new observations, but helped discover the Uranus moon in 2024.
“This new Uranus Moon is a very exciting discovery as it is very close to Uranus and is likely to be related to the inner ring system,” Shepherd said. “This discovery shows that the power of James Webbspace Telescopes can capture images more deeply than ever before.”
At the Seti Institute in Mountain View, California, Coprinpal investigator Matthew Tiscarreno, a senior research scientist at the solar system dynamics and planetary rings, said other planets have as many small inner membranes as Uranus. According to NASA, astronomers don’t know that they avoided crashing together with the tiny moons because they are so close to each other, but the satellite could act as a shepherd in Uranus’ narrow ring.
“The complex interaction with the ring, which suggests a chaotic history that blurs the line between the ring system and the lunar system, said in the statement. “And more, the new moon is smaller and far more surprising than the previously known inner moon, which could lead to more complexity being discovered.”
Before taking in the groundbreaking views of Voyager 2’s Raj in 1986, the first two, fifth discovered in 1787 and 1948, had been found orbiting the planet.
Voyager 2 found 10 months during a flyby, ranging from 16 to 96 miles (26 to 154 km) in diameter. According to NASA, Hubble and the ground telescopes discovered 13 more small moons. According to the space agency, the inner moon appears to be made of ice and rock, but the moon beyond Oberon may be captured in orbit around Uranus.
“Looking forward, this moon discovery highlights how modern astronomy continues to be built into the legacy of missions like Voyager 2, which passed Uranus on January 24, 1986, showing its first close-up in this mystical world,” Elmutamide said in a statement. “Now, almost 40 years from now, James Webb’s space telescope is pushing that frontier even further.”
Future Uranus exploration missions planned in the early 2030s could help astronomers understand the ice giants more than ever before, including orbiters and atmospheric probes.
Uranus is largely defined by the data collected during the flyby of Voyager 2, but another more detailed visit to the ice giant that spins its side is postponed to shed light on the planet’s atmospheric dynamics, complex magnetic fields, and what led to its extreme tilt and creation of the ring. A detailed observation can also reveal whether Uranus’ moon is an ice-covered ocean world.
A 10-year survey of the planet, written by the National Academy of Sciences, Engineering and Medicine in 2022, recommended the first dedicated Uranus orbiter and probe as the next large NASA mission. It is unclear where the mission will fit into NASA’s future plans, especially as agents work on the White House’s proposal to cut NASA’s scientific budget by half.
Shepherd said there is certainly an undiscovered Uranus, only a few kilometres in size, but it’s more surprising than the newly detected moon and even harder to find.
“By taking very long images on JWST or future Uranus spacecraft missions, you’ll likely find a new moon,” Shepherd said.
Second, Elmtamid and her team want to reveal details about the orbital of the new moon, search for additional moons, and support planning for Uranus orbiter and probe missions.
“Discovering a new moon around Uranus helps scientists to better understand how that strange system is formed, shedding light on the ring and preparing for future missions like NASA’s Uranus Orbiter and Probe,” Elmutamide said.
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