Astronomers Discover 128 New Moons Orbiting Saturn, Cementing the Planet’s Title of ‘Moon King’

Saturn and Jupiter have been locked in a competition for the planet with the highest number of moons. But as it happens, Jupiter never really stood a chance: Saturn has just won by a huge margin.

That’s because on Tuesday, the International Astronomical Union (IAU) recognized 128 new moons in orbit around Saturn, discovered by astronomers from Taiwan, Canada, the United States and France. Saturn’s new grand total of 274 moons is almost twice as many as all the rest of the moons in our solar system combined—so, the planet has clearly earned the title of “moon king.”

“These are small little rocks floating in space, so some people might not find it quite an achievement,” Edward Ashton, an astronomer at the Academia Sinica in Taiwan, tells New Scientist’s Matthew Sparkes. “But I think it’s important to have a catalogue of all the objects in the solar system.”

Ashton and his colleagues posted their findings as a preprint study, which has not undergone peer review, on the arXiv server on Monday.

The team monitored the space around Saturn with the Canada-France-Hawaii Telescope (CFHT) at Mauna Kea, between 2019 and 2021. They discovered the new moons with a “shift and stack” technique, which combines multiple images of a moon’s orbital path to make the celestial body bright enough to identify.

This approach had led the team to previously spot 62 other moons around Saturn back in 2023. “It was that study … which prompted the more intense search in 2023, which yielded another 128 moons,” co-author Brett Gladman, an astronomer from the University of British Columbia in Canada, tells EarthSky’s Kelly Kizer Whitt.

It’s the “largest batch of new moons,” as study co-author Mike Alexandersen, an astronomer at the Center for Astrophysics, Harvard and Smithsonian, tells the New York Times’ Jonathan O’Callaghan.

Saturn has 128 newly-discovered moons. Here they are color-coded by their MPEC release. Orange: MPEC 2025 E153, Purple: MPEC 2025-E154, Green: MPEC 2025-E155. pic.twitter.com/0aO6WXl7Ni

— Tony Dunn (@tony873004) March 12, 2025

The moons are “irregular,” approximately potato-shaped and only a few miles across. For comparison, the diameter of our moon is 2,159 miles. The newly discovered orbiters are located between about 6.5 million to almost 18 million miles from Saturn, which is much farther than Saturn’s rings and major moons.

Astronomers suspect the newly identified objects to be fragments of ancient moons that became trapped in the planet’s gravity during our solar system’s early history, then collided either with other moons or with comets, Gladman explains in a statement.

The team thus classified the moons into potential families, grouped together by a common source of fragmentation. They suspect one such family—encompassing 47 of the newly identified moons and named Mundilfari in honor of a Norse deity—fragmented at most 100 million years ago. An older collision would have seen the fragments smash each other out of existence by now, Gladman tells EarthSky. Dating the creation of these moons could shed light on early solar system dynamics as well as how Saturn’s rings may have come about.

As advancing technology enables astronomers to spot more and more orbiting objects, scholars might start calling into question what deserves to be categorized as a moon versus what might just be a big rock.

“I don’t think there’s a proper definition for what is classed as a moon. There should be,” Ashton tells the Guardian’s Hannah Devlin. For now, scientists at the IAU consider anything with a traceable orbit around a host body good enough to be a moon, as the New York Times reports.

Either way, in the future “we might want to extract resources from asteroids and moons in the solar system, so having a great understanding of what is where is important for that,” Elizabeth Day, a geophysicist from Imperial College London who was not involved in the research, tells New Scientist.

Now, the researchers are tasked with naming the 128 new moons. Saturnian moon-naming tradition calls for names based on mythological divinities, and most of these newcomers will likely be named after Viking gods—hopefully the Norse pantheon has enough deities!

Margherita Bassi | READ MORE

Margherita Bassi is a freelance journalist and trilingual storyteller. Her work has appeared in publications including BBC Travel, Discover magazine, Live Science, Atlas Obscura and Hidden Compass.