What are the names of Jupiter’s 79 moons?

Jupiter’s Moon Party: More Than Just a Giant Red Spot!

So, you know Jupiter, right? Big, stripy, has that famous red spot? Well, it’s not just a pretty face; it’s also got a whole entourage of moons! As of today, April 30, 2025, we’re talking a whopping 97 moons officially recognized by the International Astronomical Union (IAU). That’s like, a small solar system all its own! And they come in all shapes and sizes, from tiny little space rocks to Ganymede, which is seriously HUGE – the biggest moon in our entire solar system.

Let’s start with the headliners: the Galilean moons. These guys – Io, Europa, Ganymede, and Callisto – are the OGs. Back in 1610, Galileo Galilei spotted them, and BAM! It was the first time anyone realized stuff could orbit a planet other than Earth. Pretty mind-blowing for the time, huh? A German astronomer named Simon Marius also saw them around the same time, but Galileo got the credit because he shouted it from the rooftops first. Marius did suggest the names we use today, but they didn’t really stick until the 20th century. For ages, they were just called Jupiter I, II, III, and IV. How boring is that?

But these aren’t just any old moons. Each one is a total character:

• Io: Talk about a hot mess! This moon is the most volcanically active place in the solar system. Seriously, it’s like a pizza oven in space.
• Europa: Now, this one’s interesting. Scientists think it might have a giant ocean hiding under a layer of ice. Could there be life? Maybe! It’s got everyone buzzing.
• Ganymede: This moon is a straight-up overachiever. It’s bigger than the planet Mercury AND it’s the only moon with its own magnetic field. Show off!
• Callisto: Think old and beat-up. Callisto’s surface is covered in craters, like it’s been through a million space battles. And guess what? It might even have a hidden ocean too!

Okay, so the Galileans are the rock stars, but Jupiter’s got a whole support cast of smaller moons. Amalthea was the next one found, back in 1892. After that, things really picked up with photographic observations. A lot of these moons are pretty dinky, and they’ve been popping up left and right in the 20th and 21st centuries. This one guy, Scott S. Sheppard, an American astronomer, has discovered over 60 moons of Jupiter since the year 2000! Can you imagine stumbling upon a whole new moon?

Now, how do they come up with these names? Well, the IAU has a system. They usually name them after figures from Roman and Greek mythology who were connected to Jupiter (Zeus). Think lovers, friends, family – you know, the whole crew. Back in 2018, when they found a dozen new moons, the Carnegie Institution for Science even asked Twitter for suggestions! Seriously! They sent the best ones to the IAU, and we ended up with names like Pandia, Ersa, Eirene, Philophrosyne, and Eupheme. All cool characters from Greek myths. The IAU also tries to name moons based on which way they orbit.

The IAU also has some rules about naming the really tiny ones. If a moon is less than 1 km across or pretty dim, they might not bother giving it an official name unless it’s super interesting to scientists. Fair enough, right?

And get this: a lot of the outer moons are probably captured asteroids or bits and pieces from space crashes. They tend to hang out in groups, orbiting together like cosmic buddies. These groups get named after one of the moons in the bunch, like the Ananke, Carme, and Pasiphae groups. Plus, a lot of these outer moons are rebels – they orbit Jupiter backwards! We call that a retrograde orbit.

All in all, Jupiter’s moons are a wild bunch. From the big-shot Galileans to the hordes of smaller, weirder moons, they give us a peek into how our solar system formed and changed over time. And with new discoveries happening all the time, who knows what we’ll find out next? Keep looking up!