The second-largest planet in our solar system and the sixth planet relative to the sun, Saturn is a true behemoth of our grand planetary system. In fact, Jupiter’s the only planet that can top Saturn in size. Still, this particular gas giant measures about nine and a half times larger than Earth. Of course, Saturn wouldn’t be Saturn without all its dozens upon dozens of moons. But just how many moons does Saturn have? The answer isn’t so clear-cut. It’s an ever-changing, ever-shifting thing. Here’s what that means.
Discovery of Saturn’s Moons
Centuries before telescopic photography was invented, astronomers were observing Saturn’s moons. Christiaan Huygens discovered Titan, the largest of the bunch, using a simple, self-made lens and basic telescope in 1655. Astronomer Giovanni Domenico Cassini made similarly great strides not long after Huygens, spotting Tethys, Dione, Rhea, and the Sidera Lodoicea (i.e. Iapetus) throughout the 1670s and ‘80s.
Another century would lapse before astronomers would discover more of Saturn’s moons. German astronomer William Herschel spotted Mimas (a.k.a. Saturn I) and Enceladus in 1789. Then, another enormous gap until 1848, when both William Lassell and father-son duo W. C. & G. P. Bond separately discovered Hyperion (Saturn VII). Thankfully, not long after this, the world was introduced to the magic of telescopic photography. From this point forward, the number of observable moons observed around Saturn increased exponentially.
Long-exposure film was so revolutionary to the field of astronomy. It was able to capture wavelengths unseen to the naked eye through the use of special optical filters over long periods. TSaturn’s observable moons entered the double digits throughout the remainder of the late 1800s and most of the 1900s. Revolutionary space probes launched in the last quarter of the 1900s were also integral to the discovery of Saturn’s moons, uncovering even more in orbit than previously thought. By the year 2000, the total number had risen to 18 moons.
Observing Saturn’s Outer Moons
Saturn was believed to have just 18 moons by the start of the new millennium. That number has more than quadrupled in the decades since, thanks to unmanned spacecraft and state-of-the-art digital cameras to thank for this. The Cassini–Huygens mission was launched toward Saturn in 1997 and finally arrived tn 2004. The space probe remained in Saturn’s orbit for the next 13 years, circling around and around until 2017.
This single spacecraft discovered more than half a dozen additional moons. Meanwhile, astronomers continued to observe Saturn and its moons from the Earth via telescope. In 2000, more than four dozen moons joined the list, all discovered using telescopes on the ground. While the Cassini-Huygens continued to orbit, astronomers on Earth searched the skies from afar. By the close of the first decade of the 21st century, dozens more were added to that total.
Astronomers believed that Jupiter had the most moons in the solar system. However, towards the end of the 2010s, Saturn officially surpassed Jupiter’s numbers. More discoveries still happen to this day, with the most recent being announced in 2021. Saturn’s total has risen to more than 80. The International Astronomical Union has confirmed and named 63 of these moons, with another 20 awaiting official confirmation and naming by the IAU.
Saturn’s Major Moons
Of these 83 moons discovered around Saturn to date, seven moons make up 99.96% of the total mass in orbit. The other 76 moons account for a paltry 0.04%! These seven — Titan, Rhea, Iapetus, Dione, Tethys, Enceladus, and Mimas — are what’s known as Saturn’s major moons. Let’s break down all there is to know about these seven below, including diameter, discovery date, and more. Then, after that, we’ll briefly discuss the remaining 76.
|Titan||VI||5149.46 km||1655||Huygens||+15.9 days|
|Rhea||V||1527.6 km||1672||Cassini||+4.5 days|
|Iapetus||VIII||1468.6 km||1671||Cassini||+79.3 days|
|Dione||IV||1122.8 km||1684||Cassini||+2.7 days|
|Tethys||III||1062.2 km||1684||Cassini||+1.8 days|
|Enceladus||II||504.2 km||1789||Herschel||+1.3 days|
|Mimas||I||396.4 km||1789||Herschel||+0.9 days|
The Orbital Groups of Saturn
Now that we’ve accounted for the majority of Saturn’s total mass in orbit — all 99.96% of it — let’s take a closer look at the remaining 76 moons sharing that 0.04% of remaining mass in orbit. Once all is said and done, we’ll have a clear picture of just how many moons Saturn has. Not to mention the variety of different shapes, sizes, and types of moons circling Saturn today. While this number may — and likely will — change after the date of this publication, this is everything we know about Saturn’s moons as of this writing.
Ring moonlets make up an interesting little orbital group around Saturn. They consist of hundreds of tiny moon-like objects, with the vast majority not officially considered moons. They mostly range from a few meters in diameter to as much as several kilometers across. If one had to wager an educated guess, it’s widely believed these ring moonlets come from larger moons that were torn apart into smaller chunks. While they might not be official moons, they nevertheless play a key role in forming and shaping Saturn’s rings.
Also referred to as shepherd satellites, Saturn’s ring shepherds are mini-moons that orbit around the edge of the planet’s system of rings. They exist to fill in the gaps between rings, helping to add shape to their edges. (Much like how a good shepherd would keep their sheep confined.) Ring shepherds do the same to Saturn’s ring particles: They keep the bands narrow, and they prevent the particles from spreading out too far beyond their reach. While there is a handful that falls under this category, the most notable of the bunch are Pandora and Prometheus.
This orbital group consists of just two major players: Janus and Epimetheus. These co-orbitals are more or less the same size, give or take around 60 kilometers in diameter. (Janus is the larger of the two, for the record.) They’re called co-orbitals because they actually swap orbits with each other every four years. This flip-flopping happens because their orbital path is the same. However, they don’t ever run the risk of a collision because of the many kilometers that separate them. Instead, they merely trade off with one another.
Remember Dione, Tethys, Enceladus, and Mimas from our discussion of Saturn’s major moons? These four are also known as the inner large orbital group. This quartet of moons has a lot in common: They all have heavily cratered surfaces, and they’re all mostly filled with water ice. A couple of these inner larges remain geologically alive: Dione and Enceladus. With that being said, Dione’s geological life is much less significant than that of Enceladus. (Enceladus also happens to be the smallest known body in the entire solar system to have geological life.)
Saturn’s moons Methone, Anthe, and Pallene make up what scientists refer to as the Alkyonides. Named after the daughters of Alcyone, a figure from Greek mythology, the Alkyonides are irregularly shaped, heavily cratered moons that orbit between inner larges Mimas and Enceladus. Collectively, these three Alkyonides account for some of the tiniest masses in all of Saturn’s 80+ moons. For example, the smallest Alkyonide Pallene is just 2.6 kilometers in diameter — just over a mile and a half in all.
You wouldn’t be able to answer the question “How many moons does Saturn have?” without the Trojan moons. Throughout the entire solar system, there’s no other planet with a system like the Trojans. These are small group of moons that orbit 60 degrees ahead of or behind a larger moon. The most notable is Telesto, which tails Tethys of the inner larges. As it happens, Tethys actually has two trojans moons: the aforementioned Telesto in the leading position and then Calypso in the trailing position.
On the flip side of the inner larges, we have the outer larges. This orbital group is made up of the other three major moons: Titan, Iapetus, and Rhea. In addition to being further away from Saturn than the other orbital groups, the outer larges also have more complex surfaces than their inner large counterparts. They’re covered in mountains, valleys, lakes, clouds, and other interesting features that can’t be found in other orbital groups of Saturn’s moons. All in all, these outer larges are Saturn’s biggest moons by far.
Lastly, we have the irregulars. Of all 83 of Saturn’s moons, more than 70% of them belong to this orbital group. Likewise, this orbital group is largely responsible for the ever-changing number of moons surrounding Saturn. This is because the irregulars consist of dozens of highly elliptical, extremely irregular orbits. Astronomers believe these irregulars mainly comprise asteroids and comets that got caught in Saturn’s gravitational pull. Numerous irregulars have come and gone, and this pattern will undoubtedly continue forever.
How Many Moons Does Saturn Have?
As of this writing, the number sits at a whopping 83. It’s fascinating to see how much this number has changed in just the past 20 years, let alone the past two centuries. Because Saturn is so massive and its gravitational pull is so strong, astronomers still think this number will continue to change over time and observational technology grows more advanced. For the time being, however, the number of Saturn’s moons is a record-setting 83.
The image featured at the top of this post is ©Vadim Sadovski/Shutterstock.com.