When we look up at the night sky, we see our one Moon. It is a familiar, constant companion. But when we look at the giant of our solar system, Jupiter, the story is completely different. Jupiter is not just a planet; it’s the center of its own massive system, almost like a mini solar system. It is the king of the planets, and it has a royal court of moons that is almost too large to count.
For hundreds of years, we thought we had a good idea of Jupiter’s family. First, we knew of four, then a dozen, then a few dozen more. But in the last few years, and especially with recent discoveries, that number has suddenly jumped. The old textbooks are now officially out of date.
Scientists using powerful new telescopes are finding new, tiny moons orbiting this giant world all the time. It seems that the more we look, the more we find. This raises a big question: just how many moons does Jupiter actually have right now, and why does this number keep changing?
What is the Official Moon Count for Jupiter in 2025?
As of 2025, the official count of Jupiter’s confirmed moons is 97. This is an amazing number, and it has made headlines recently. For a long time, Saturn held the record for the most known moons, but Jupiter’s count has been growing fast as astronomers confirm new discoveries. Just a couple of years ago, the number was 95, which itself was a big jump from the 79 moons we had cataloged before that.
The new moons that were recently confirmed—bringing the total from 95 to 97—are just like the other recent discoveries. They are not giant, round worlds. Instead, they are very small, probably only a mile or two across. They are also very far away from Jupiter, with wild, tilted orbits.
It is important to use the word “confirmed.” This means astronomers have watched these objects for long enough to be 100% sure that they are in a stable orbit around Jupiter and are not just passing asteroids. Scientists believe there are hundreds of other, even smaller objects (sometimes called “moonlets”) orbiting Jupiter, but they are too small or too dark to be found and tracked with our current technology. So, while 97 is the official number today, you can be almost certain that this number will go up again.
Who First Discovered Jupiter’s Moons?
For almost all of human history, we believed Jupiter was just a bright, wandering star in the sky. That all changed in 1610. An Italian astronomer named Galileo Galilei built one of the first telescopes and pointed it at Jupiter. What he saw changed our world forever.
He did not just see the planet. He saw four tiny, bright dots of light in a near-perfect line on either side of it. He watched them night after night. He saw that they were moving, and they were moving around Jupiter. This was a revolutionary, and dangerous, idea. At the time, most people believed that everything in the universe, including the Sun and planets, orbited the Earth.
Galileo’s discovery showed that this was not true. Here were four “stars” clearly orbiting another planet. This was powerful proof that the Earth was not the center of everything. These four big moons are known today as the Galilean moons in his honor. They are the biggest and brightest of Jupiter’s family, and you can still see them for yourself from your backyard with a good pair of binoculars or a small telescope. They look just like tiny pinpricks of light, exactly as they did to Galileo over 400 years ago.
What Are the Four Big “Galilean” Moons Like?
The 97 moons are not all equal. Four of them are massive, planet-sized worlds, while the other 93 are tiny, captured rocks. The four Galilean moons are the most famous, and each one is a unique and fascinating place. Spacecraft have studied them up close, and they are the main targets for new missions.
First is Io (pronounced “EYE-oh”). Io is the ultimate “bad boy” of the solar system. It is the most volcanically active body we have ever seen. Its surface is not covered in craters from impacts, because any craters get filled in almost immediately. Instead, it is covered in hundreds of active volcanoes that erupt massive plumes of sulfur and other materials, painting the surface in strange shades of yellow, red, and black. It looks like a giant, moldy pizza. This extreme volcanism is caused by Jupiter. Io is so close to the giant planet that Jupiter’s immense gravity constantly squeezes and stretches it, like bending a paperclip back and forth. This process, called tidal heating, generates massive amounts of heat inside Io, which escapes through its volcanoes. Just in late 2024 and early 2025, NASA’s Juno spacecraft made daring, close flybys of Io, finding evidence of “still-warm” magma just under the surface, showing us this world is even more active than we imagined.
Next is Europa. Europa is one of the most exciting places in the entire solar system because it is a top target in the search for life. On the outside, Europa is a bright white world, covered in a shell of extremely hard, cold water ice. This ice shell is smooth but is crisscrossed with long, dark cracks and ridges, making it look like a giant, fractured eggshell. The exciting part is what lies beneath the ice. Scientists are almost certain that Europa hides a massive, global ocean of liquid saltwater. This hidden ocean may contain more than twice as much water as all of an Earth’s oceans combined. Where there is liquid water, energy (from the same tidal heating that powers Io), and chemical nutrients (which could come from the moon’s rocky seafloor), you have the three main ingredients for life. We do not know if anything is living there, but it is the best place to look.
Then there is Ganymede. Ganymede is the king of moons. It is the largest moon in our entire solar system, bigger than the planet Mercury and the dwarf planet Pluto. If it were orbiting the Sun on its own, it would easily be classified as a planet. Ganymede is a complex, icy world. Like Europa and Callisto, it is also believed to have a salty ocean deep beneath its surface, but it is likely buried under a much thicker layer of ice. Ganymede’s most unique feature is that it is the only moon in the solar system known to have its own magnetic field. A magnetic field (like Earth’s) acts as a protective shield against radiation. Ganymede’s field creates its own mini “auroras” (like our northern lights) at its poles.
Finally, there is Callisto. Callisto is the most distant of the four Galilean moons. Its surface is the oldest and most heavily cratered of any object in our solar system. It looks like it has been in a cosmic boxing match for billions of years and has the scars to prove it. Because it is farther from Jupiter, it experiences less tidal heating, so its surface is “dead” and has not been recycled by volcanoes or tectonic activity like the other moons. This makes it a perfect time capsule, showing us what the solar system was like billions of years ago. Like Ganymede and Europa, Callisto may also have a deep, hidden ocean, but it is likely buried under hundreds of miles of ice.
Why Does Jupiter Have So Many Moons?
Jupiter’s massive collection of moons exists for two main reasons, and it all comes down to one thing: its incredible size. Jupiter is more than twice as massive as all the other planets in our solar system combined. This gives it a gigantic gravitational pull that dominates its neighborhood.
The first reason is formation. The four big Galilean moons were likely born with Jupiter. When Jupiter was forming from a giant cloud of gas and dust, a smaller disk of material collected around it. This “mini solar system” of gas and dust eventually clumped together to form the large, round moons we see today: Io, Europa, Ganymede, and Callisto. They orbit in a nice, flat plane, and all travel in the same direction, just like the planets orbit the Sun.
The second reason is capture. This is where the other 93 moons come from. These moons were not born with Jupiter. They were once asteroids and comets flying through the solar system. They came too close to the giant planet and were captured by its powerful gravity, forced into a permanent orbit. This is why Jupiter is sometimes called the “vacuum cleaner of the solar system.” Its gravity is so strong that it sweeps up and captures debris. This explains why these moons are so different from the Galilean ones.
What Are All These New “Irregular” Moons?
The 93 other moons—including all the new ones discovered recently—are known as “irregular moons.” They are nothing like the big four. They are small, lumpy, and look more like potatoes or asteroids than round worlds. The largest of them is only about 100 miles (170 km) across, and most are just a few miles wide.
What really makes them “irregular” is their orbits. While the big moons orbit in neat, flat, circular paths, the irregular moons have wild and strange orbits. Their orbits are often very elongated (oval-shaped) and highly tilted. This means they do not orbit around Jupiter’s equator; they swing high above and far below the planet.
The most fascinating part is that many of them orbit backwards. This is called a “retrograde” orbit. They travel in the opposite direction to Jupiter’s spin and the orbits of its main moons. This is a dead giveaway that they were captured. It is almost impossible for a moon to form spinning backward. The only way it happens is if it was a passing object that got snagged by Jupiter’s gravity. Astronomers group these irregular moons into “families” based on their similar orbits. They believe these families are the broken-apart pieces of larger asteroids that were captured by Jupiter and then shattered by collisions millions or billions of years ago.
How Do Scientists Find New Moons Today?
You might think that finding a new moon is as simple as looking through a telescope. But the moons that are being discovered now are unbelievably small, dark, and far away. Finding one is like trying to spot a piece of coal from a hundred miles away, while it is moving.
Astronomers like Scott Sheppard, who has led the teams that found most of these new moons, use some of the largest and most powerful telescopes on Earth. These are often located on high mountaintops in places like Hawaii and Chile, where the air is very clear and dark.
The process is long and difficult. First, they use a special camera on the telescope to take many pictures of the sky around Jupiter over several nights. Then, they use powerful computers to look for tiny dots of light that are moving relative to the background stars. The distant stars stay in fixed patterns, but an object orbiting Jupiter will move with the planet across the sky.
Once they find a “candidate” moon, the real work begins. They have to track this tiny dot for months, and sometimes even years, to map its full orbit. They must prove that it is truly locked in orbit around Jupiter and not just a passing asteroid. Only after its orbit is confirmed does it get an official designation (like S/2022 J 1) and get added to the official count. This long confirmation process is why we sometimes get announcements of a dozen new moons all at once, even though they were first spotted over different years.
Are We Sending Spacecraft to Visit These Moons?
Yes! While the tiny irregular moons are too small and distant to visit easily, the big Galilean moons are some of the hottest destinations in the solar system. Right now, three major missions are focused on Jupiter’s system.
First is NASA’s Juno spacecraft, which is already at Jupiter. While its main job was to study the planet itself, its mission has been extended. In late 2024 and early 2025, it made a series of incredibly close flybys of the volcanic moon Io, giving us the best new data we have had on that fiery world in over 20 years.
Second is the European Space Agency’s JUICE mission (which stands for JUpiter ICy Moons Explorer). It launched in April 2023 and is currently on a long journey. It just completed a gravity-assist flyby of Venus in August 2025 to help it gain speed. When it arrives at Jupiter in 2031, it will study Europa and Callisto, but its main target is Ganymede. In 2034, it will become the first spacecraft in history to orbit a moon other than our own.
Third is NASA’s Europa Clipper mission. This is a very exciting one. It launched in October 2024 and is also on its way, having just completed its Mars flyby in March 2025. It will arrive at Jupiter in 2030 for one main purpose: to find out if Europa’s hidden ocean could really support life. It will not orbit Europa directly (which is difficult because of Jupiter’s intense radiation), but it will orbit Jupiter and perform nearly 50 close, low-altitude flybys of Europa. It will use ice-penetrating radar to measure the thickness of the ice shell and confirm the ocean’s existence, and it will even fly through any water plumes that might be erupting from the surface to “taste” the water for chemical signs of life.
Will We Find Even More Moons at Jupiter?
The answer to this is a definite yes. The 97 moons we know about in 2025 are just the ones we can find with today’s technology. Astronomers are almost certain that there are hundreds, and perhaps thousands, of smaller “moonlets” orbiting Jupiter, objects that are less than a mile wide.
As our telescopes on Earth get more powerful, like the new Vera C. Rubin Observatory being built in Chile, we will be able to see fainter and smaller objects. These new tools will scan the sky more deeply and quickly than ever before. It is very likely that in the next five to ten years, we will see another big jump in Jupiter’s moon count.
So, while 97 is the answer for today, it is really just a snapshot in time. Jupiter’s family is far larger than we can see, and we are only just beginning to complete the census. The king of the planets still has many secrets left to reveal.
Conclusion
Jupiter is far more than just a single planet; it is a complex and massive system. Its family of 97 confirmed moons is a beautiful example of our solar system’s diversity. This family is dominated by four giant, planet-like worlds, each one a unique and fascinating target for exploration. But it also includes 93 other small, captured, irregular moons that tell a very different story—a story of the solar system’s chaotic past.
Thanks to powerful telescopes and new robotic explorers like Europa Clipper and JUICE now on their way, our knowledge of this system is growing every year. The moon count keeps ticking up as we find new, tiny members of the family. These discoveries are not just about counting; they are about understanding how our solar system formed and, most exciting of all, whether life could exist on an icy ocean world far from the Sun.
As we continue to explore Jupiter’s moons, what do you think is the more exciting possibility: finding simple forms of life in Europa’s ocean, or discovering that a world as big as Ganymede could also be habitable?
FAQs – People Also Ask
What is the biggest moon in the solar system?
The biggest moon in our solar system is Jupiter’s moon Ganymede. It is even larger than the planet Mercury and the dwarf planet Pluto. If it were orbiting the Sun by itself, it would be considered a planet.
How many moons does Saturn have in 2025?
As of 2025, Saturn is the “moon king” with 146 known moons. For a while, Jupiter’s count was higher, but recent discoveries at Saturn have put it back in the lead. Both planets likely have many more tiny, undiscovered moons.
Can you see Jupiter’s moons from Earth?
Yes, you can! The four largest moons—Io, Europa, Ganymede, and Callisto—are bright enough to be seen from Earth with a good pair of binoculars or any small telescope. They will look like four small, star-like dots in a line next to the bright planet.
Why does Earth only have one moon?
Our Moon is very large compared to the size of Earth. The most popular theory is that a giant, Mars-sized object smashed into the young Earth billions of years ago. The debris from this massive collision was thrown into orbit and eventually came together to form our Moon.
What is a retrograde moon?
A retrograde moon is one that orbits its planet in the opposite direction of the planet’s rotation. Many of Jupiter’s small, irregular moons are retrograde. This is strong evidence that they did not form with Jupiter but were captured by its gravity.
What is the Europa Clipper mission?
Europa Clipper is a NASA spacecraft that launched in 2024 and will arrive at Jupiter in 2030. Its main goal is to study Jupiter’s moon Europa by performing dozens of close flybys to see if its hidden, subsurface ocean of liquid saltwater has the right conditions for life.
What is the JUICE mission?
JUICE is a European Space Agency (ESA) spacecraft that launched in 2023. It will arrive at the Jupiter system in 2031 to study three of the icy moons: Ganymede, Callisto, and Europa. In 2034, it will become the first spacecraft to ever orbit another planet’s moon (Ganymede).
Why is Jupiter’s moon Io so full of volcanoes?
Io is the most volcanically active body in the solar system. This is caused by “tidal heating.” Io is in a gravitational tug-of-war between the massive Jupiter and the other large moons. This constant pulling and stretching flexes the moon, generating enormous heat in its interior, which escapes through volcanoes.
What is an irregular moon?
An irregular moon is typically small, has a strange “lumpy” shape, and has a large, tilted, and often “backward” (retrograde) orbit. These moons were not formed with their planet but were instead asteroids or comets that were captured by the planet’s gravity. Most of Jupiter’s 97 moons are irregular.
How do moons get their names?
New moons are first given a temporary name, like S/2022 J 1. Once their orbit is 100% confirmed, the International Astronomical Union (IAU) is responsible for naming them. For Jupiter, most moons are named after characters from Greek mythology who were lovers or descendants of the god Zeus (the Greek name for Jupiter).