You probably think you know Saturn. It’s the one with the rings, right? The "jewel of the solar system." But honestly, when we talk about what is the second biggest planet, the sheer scale of the thing is hard to wrap your head around. It’s a massive, swirling ball of gas that would technically float in a bathtub—if you had one big enough to fit a planet 760 times the volume of Earth.
Saturn is big. Really big. It’s about 74,898 miles (120,536 kilometers) wide at its equator. To put that into perspective, you could line up nine Earths side-by-side and they still wouldn’t quite reach across Saturn’s middle. Yet, despite being a total heavyweight in terms of size, it’s remarkably light for its stature.
Why the Second Biggest Planet is a Cosmic Lightweight
The most mind-blowing thing about Saturn isn’t just its size; it’s the density. Or lack thereof. It’s the only planet in our solar system that is less dense than water. If you dropped it into a giant cosmic ocean, it would bob like a cork. Basically, it’s a giant balloon made of hydrogen and helium.
Jupiter is the undisputed king of size, but Saturn isn't far behind in terms of diameter. However, when it comes to mass, Jupiter is more than three times as heavy. This difference comes down to how these giants formed. Saturn is mostly "fluff"—molecular hydrogen and helium—with a hot, rocky core deep inside that's probably about the size of Earth but way more massive.
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The Shape of a Speedster
Because Saturn rotates so fast—a day there only lasts about 10.7 hours—it’s actually noticeably squashed. Astronomers call this being "oblate." It spins so quickly that it bulges at the equator and flattens at the poles. It’s not a perfect sphere. It’s more like a basketball that someone is sitting on. This rapid spin also drives some of the most intense winds in the solar system, reaching up to 1,100 miles per hour. That's faster than a jet fighter.
The Ring System: More Than Just Decoration
When you ask what is the second biggest planet, the rings are usually the first thing that comes to mind. But here’s the kicker: they aren’t solid. Not even close. They’re made of billions of individual chunks of ice and rock. Some are as small as a grain of sand; others are the size of a mountain.
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These rings are incredibly wide—spanning about 175,000 miles—but they are hauntingly thin. In most places, they are only about 30 feet (10 meters) thick. Imagine a sheet of paper that’s miles wide but still just a fraction of an inch thick. That’s the scale we’re talking about.
Where Did They Come From?
Scientists are still arguing about this. One leading theory is that a moon got too close to Saturn and was torn apart by the planet’s gravity. Another idea is that they are leftovers from when the solar system formed 4.5 billion years ago. However, data from the Cassini mission suggests the rings might be much younger than the planet itself—maybe only 10 to 100 million years old. If that's true, the dinosaurs might have looked up and seen a Saturn without rings.
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The Moons: Where the Real Action Is
If Saturn is the "second biggest planet," it’s also the king of the "mini-solar systems." As of 2026, we’ve confirmed 146 moons orbiting this giant. Some are just tiny rocks, but others are world-class mysteries.
- Titan: It’s bigger than the planet Mercury. It has a thick atmosphere and lakes of liquid methane. It’s the only other place in the solar system with stable liquid on its surface.
- Enceladus: This tiny ice ball is shooting geysers of water into space. Under its frozen crust lies a global salt-water ocean that might—just might—harbor life.
- Mimas: It looks exactly like the Death Star from Star Wars thanks to a massive crater named Herschel.
The Hexagon at the Pole
At Saturn's north pole, there is a literal six-sided storm. It’s a massive jet stream that has maintained a perfect hexagonal shape for decades. Each side of the hexagon is wider than Earth. We still don't fully understand how it stays so perfectly geometric without breaking apart into a circle like every other storm in the universe.
Exploring the Giant in 2026 and Beyond
We aren't done with Saturn. Not by a long shot. While the Cassini mission ended in 2017 with a dramatic plunge into the planet's atmosphere, the data it sent back is still being analyzed today.
Looking ahead, NASA’s Dragonfly mission is the next big thing. It’s a literal drone—a rotorcraft—that will fly across the surface of Titan. Launching later this decade, it aims to search for the chemical building blocks of life. Because Saturn isn't just a big planet; it's a laboratory for understanding how life might start on other worlds.
Actionable Insights for Space Enthusiasts
If you want to experience the second biggest planet for yourself, you don't need a billion-dollar probe. Saturn is one of the few planets easily visible to the naked eye. It looks like a bright, yellowish "star" that doesn't twinkle.
- Get a telescope: Even a basic backyard telescope (around 25x magnification) will reveal the rings. It is, honestly, one of the most moving things you can see with your own eyes.
- Check the Opposition: Look for "Saturn at Opposition" dates. This is when Earth is directly between the Sun and Saturn, making the planet appear its largest and brightest in our sky.
- Follow the Dragonfly Mission: Keep an eye on updates from NASA’s Jet Propulsion Laboratory (JPL) regarding the Titan drone. It’s going to change everything we know about "habitability."
Saturn is more than just a runner-up to Jupiter. It’s a complex, ringed world that challenges our understanding of physics, chemistry, and the potential for life beyond Earth. Whether you're looking at its hexagonal storms or its ice-spewing moons, the second biggest planet remains the most fascinating neighbor we have.