With astronomers officially discovering 128 new moons, Saturn has solidified its status as a planet with the largest known family of moons. After years of observations by an international research team from Taiwan, Canada, the United States and France, the findings were officially recognized by the International Astronomical Union (IAU) on March 11, 2025.The newly discovered objects, all small, irregular moons, are giving scientists new clues about Saturn’s violent past and the collisions that shaped its system of moons billions of years ago. A study published by the American Astronomical Society titled “128 new irregular satellites of Saturn discovered” pointed out that these findings also provide new clues to the evolution of Saturn’s irregular natural satellite groups and provide a clearer picture of the changes in Saturn’s satellite system over billions of years.
How astronomers discovered 128 previously unknown moons around Saturn
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The findings were made using the Canada-France-Hawaii Telescope (CFHT), where researchers repeatedly observed the region around Saturn between 2019 and 2021. Rather than relying on a single observation, they combined multiple images to enhance the signal from extremely faint objects, allowing them to detect previously unseen satellites.Initial surveys identified 64 satellites, but also discovered many other objects that have not yet been formally identified. “We knew these were likely satellites and that there were probably more to be discovered, so we revisited the same area of the sky for three consecutive months in 2023,” said lead researcher Dr. Edward Ashton, a postdoctoral fellow at Academia Sinica’s Institute of Astronomy and Astrophysics and a Ph.D.“Sure enough, we discovered 128 new moons. Based on our predictions, I thought Jupiter would never catch up,” said Dr. Edward Ashton.
what makes these newly discovered satellite different
Unlike Saturn’s larger, better-known moons, the newly discovered objects are irregular moons.Scientists believe these moons did not form with Saturn. Instead, they were captured by planets early in the solar system’s history and then torn apart by violent collisions.Dr. Brett Gladman, a professor in the Department of Physics and Astronomy at the University of British Columbia, said: “They are only a few kilometers in size and are likely all fragments of a small number of originally captured moons that were shattered by violent collisions with other Saturnian moons or passing comets.”
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 large moons. Researchers say the unusually high number of small objects suggests a major collision occurred somewhere within the Saturn moon system in the past 100 million years. Although this sounds ancient, on astronomical time scales it is considered relatively new.Dr. Gladman explained that if the collision had happened earlier, the fragments would have continued to collide with each other until many of them were gone. Instead, the large number of surviving moonlets suggests this was a recent event.Researchers believe the collision likely occurred near the Mond Farrid subgroup of Saturn’s irregular moons. Many of the newly discovered moons are concentrated in this region, making it the strongest candidate for an ancient impact site.Dr Gladman said: “These studies show that more than 4 billion years ago, when the giant planets formed, they captured some medium-sized moons, and that the moons we see now are mostly fragments of those original captured moons.”
Years of observations change Saturn’s moon count
The latest discovery is the result of a carefully planned observation campaign spanning several years.By repeatedly studying the same areas of space and combining multiple observations, astronomers are able to identify objects not visible in a single image.“Our carefully planned multi-year campaign has produced a large number of new satellites that tell us about the evolution of Saturn’s population of irregular natural satellites,” said Dr Ashton. The international research team also included Dr Mike Alexanderson of the Harvard-Smithsonian Center for Astrophysics and Dr Jean-Marc Pettit of the Observatory of Besançon in France.
