Gas giant Saturn has significantly extended its “who has the most moons in the Solar System” competition, with 11 more moons being added to its tally. Meanwhile, Jupiter has finally cracked 100, with the discovery of four new moons orbiting our Sun’s largest planet.

The first moons around both gas giants were a little easier to spot. In 1610 CE, Galileo Galilei used a telescope of his own creation to observe Jupiter, finding what we now term the “Galilean moons”: Io, Europa, Ganymede, and Callisto. In 1655, Christiaan Huygens, again using a telescope of his own design, attempted to observe the rings of Saturn, but instead found Titan, the second-largest moon in the Solar System behind Ganymede.

After that, and a few more discoveries of moons around Saturn, there was a bit of a new moon lull. The next moons around Jupiter, for example, were not discovered until 1892. This was not due to a lack of interest, but because of the limits of telescopes, and the size of the moons themselves.

For an object to qualify as a moon, it must be on a relatively stable orbit around an object that is not a star. The objects must also have significantly different masses, with objects of similar mass orbiting each other. For instance, while Charon is largely considered Pluto’s moon, some have pushed for it to be reclassified as a double planet. There is no lower limit to how small a moon can be. As long as it is in a relatively stable orbit around a parent planet, it is a moon, although sometimes we refer to smaller moons as “moonlets”, largely because of how adorable it sounds.

As telescopes and methods have improved, we have found a lot more moons around Jupiter and Saturn. The killer blow to Jupiter for Saturn to take the “most moons” title came in 2025, when the International Astronomical Union (IAU), the body responsible for officially recognizing new moons as well as naming them, added a whopping 128 moons to the moon tally. From 2019 to 2021, the Canada France Hawaii Telescope (CFHT) monitored Saturn and its surrounding environment, spotting many moons, as well as a number of objects that were likely moons, but couldn’t be confirmed at the time, given the quality of the observations at hand.

“With the knowledge that these were probably moons, and that there were likely even more waiting to be discovered, we revisited the same sky fields for three consecutive months in 2023,” lead researcher Dr Edward Ashton, a postdoctoral fellow at the Institute for Astronomy and Astrophysics at Academia Sinica, said in a statement at the time.

“Sure enough, we found 128 new moons. Based on our projections, I don’t think Jupiter will ever catch up.”

With the latest announcement from the IAU’s Minor Planet Center, Jupiter’s total number of moons has gone up to 101. With so many moons, Jupiter’s new additions do not have any fancy names and are listed as: S/2011 J 4, S/2011 J 5, S/2018 J 5, and S/2024 J 1. As you can probably tell from their names, these objects were discovered in 2011, 2018, and 2024, but have only been confirmed now with further observations. 

As EarthSky points out, it is actually a rule not to give names to these moons. 

“While there should be no size limit below which a Jovian or Saturnian satellite must not be named,” the IAU explains, “a Jovian or Saturnian satellite with an absolute magnitude H_V fainter than 16.5 should only be named if it is of special scientific interest.”

Similarly small and faint, none of Saturn’s 11 new moons have been given more interesting names, either. Though the new discovery has brought Saturn’s total to a whopping 285 moons, Saturn’s new additions have been designated: S/2020 S 45, S/2020 S 46, S/2020 S 47, S/2020 S 48, S/2023 S 51, S/2023 S 52, S/2023 S 53, S/2023 S 54, S/2023 S 55, S/2023 S 56, and S/2023 S 57. In fact, only 63 of Saturn’s moons have names; that’s just 22 percent of its total. 

The moons of the Solar System leaderboard, as it currently stands, is:

Saturn: 285Jupiter: 101Uranus: 28Neptune: 16Mars: 2Earth: 1Venus and Mercury: 0

In short, around 66 percent of our Solar System’s moons are orbiting the gas giant Saturn, and 23 percent are orbiting Jupiter. Unless there are a lot of objects hiding around Uranus somewhere, it is unlikely that these two will be knocked off their top spots.