Saturn has strengthened its position as the planet with the largest known family of moons after astronomers officially discovered 128 new moons. The discoveries were officially recognized by the International Astronomical Union (IAU) on March 11, 2025, after years of observations conducted by an international team of researchers from Taiwan, Canada, the United States and France.The newly discovered objects are all small, irregular moons, providing scientists with new clues about Saturn’s violent past and the collisions that shaped its moon system billions of years ago. A study published by the American Astronomical Society titled “128 New Irregular Moons of Saturn Discovered” notes that the findings also shed new light on the evolution of Saturn’s irregular natural satellite populations, providing a clearer picture of how the planet’s moon system has changed over billions of years.
How did astronomers discover 128 previously unknown moons around Saturn?
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The discoveries were made using the Canada-France-Hawaii Telescope (CFHT), where researchers repeatedly observed the region around Saturn between 2019 and 2021. Instead of relying on single observations, they combined multiple images to strengthen signals from very faint objects, allowing them to discover previously unseen moons.This initial survey confirmed the presence of 64 moons, but also revealed many additional objects that have not yet been officially identified.
“Knowing that these were probably moons, and that there were likely more moons waiting to be discovered, we revisited the same sky fields for three consecutive months in 2023,” said lead researcher Dr. Edward Ashton, a postdoctoral fellow at the Institute of Astronomy and Astrophysics at Academia Sineca, who completed his PhD in astronomy at the University of British Columbia.Dr. Edward Ashton said: “It is certain that we have found 128 new moons. Based on our expectations, I do not think Jupiter will ever catch up.”
What makes these Newly discovered moons various
Unlike Saturn’s larger, better-known moons, the newly identified objects are all irregular moons.Scientists believe that these moons were not formed next to Saturn. Instead, they were captured by the planet early in the solar system’s history before being pulled apart by powerful collisions.“They are a few kilometers in size and are likely all parts of a smaller number of moons originally captured that broke up due to violent collisions, either with other moons of Saturn or with passing comets,” said Dr. Brett Gladman, a professor in the Department of Physics and Astronomy at the University of British Columbia.
An ancient collision may have created many of Saturn’s smallest moons
One of the biggest questions surrounding Saturn’s irregular moons is why there are so many small moons compared to larger moons. According to the researchers, the unusually large number of small objects indicates that a major collision occurred somewhere within Saturn’s moon system during the past 100 million years. Although this sounds ancient, it is relatively recent on astronomical time scales.Dr. Gladman explained that if the impact had occurred much earlier, the fragments would have continued to collide with each other until many of them had disappeared. Instead, the large number of remaining small moons indicates a more recent event.Researchers believe the collision likely occurred near the Mondelvari subgroup of Saturn’s irregular moons. Many newly discovered moons are concentrated in this region, making it the strongest candidate for an ancient impact site.“These studies reveal that the giant planets captured some medium-sized moons more than 4 billion years ago when the giant planets formed, and now we’re seeing moons that are mostly parts of those moons that were originally captured,” Gladman said.
Years of observations have changed the number of Saturn’s moons
The latest discoveries are the result of a carefully planned monitoring campaign spanning several years.By repeatedly studying the same regions of space and combining multiple observations, astronomers have been able to identify objects that would otherwise remain invisible in individual images.“Our carefully planned multi-year campaign has yielded a wealth of new moons that tell us about the evolution of Saturn’s irregular natural satellite clusters,” Dr Ashton said. The international research team also included Dr. Mike Alexandersen from the Harvard-Smithsonian Center for Astrophysics and Dr. Jean-Marc Petit from the Besançon Observatory in France.