Chapter 1: Welcome to the Galaxy

Step outside on a clear night, far from bright streetlights or glowing windows, and look up. What you’ll see is a sky sprinkled with stars. Some are bright. Some are faint. Some seem to twinkle. But what you're really seeing is just the tiniest piece of something enormous.

That "something" is called a galaxy.

Let’s break it down. A galaxy is a huge group of stars held together by gravity. But not just stars—there’s gas, dust, and mysterious stuff we can’t even see called dark matter. Some galaxies have hundreds of billions of stars in them. Ours is one of those. It's not a tiny star collection. It’s a gigantic, swirling city of stars, and we’re living inside it.

Even though galaxies are made up of stars, they’re not just messy clumps of them tossed into space. They have structure. Shape. Movement. Think of a galaxy like a giant neighborhood where stars live—but instead of houses on a street, you’ve got star systems spinning around a common center.

Our galaxy has a name. But that comes later. First, let’s stick with the big picture.

If you could float way, way above everything—like far above Earth, past the Moon, and way beyond Pluto—and look back at our galaxy, you wouldn’t see it as a pile of stars. You’d see a massive spiral, like a pinwheel or a whirlpool in water. Arms stretching out in all directions. A glowing center. A dark outer edge where things start to thin out.

It’s not just beautiful. It’s mind-blowing.

Galaxies come in different shapes. Some are spirals like ours, with long arms spinning around a center. Others are round like basketballs. Some look like smashed-up clouds. Astronomers—people who study space—group them into categories: spiral, elliptical, and irregular. That helps them understand how they formed and how they behave. Our galaxy, the Milky Way, is a spiral. One of the grandest kinds.

But even the word “galaxy” has an interesting origin. It comes from the Greek word galaxias, which means “milky.” Thousands of years ago, people noticed a faint, milky-looking band stretching across the sky. No one knew what it was, but it was too bright and too smooth to be just regular stars. They called it the “milky path,” or “milky circle.” That name stuck, and today we call it the Milky Way. But back then, they didn’t know it was a galaxy. In fact, they didn’t even know galaxies existed.

For a long time, everyone thought the Milky Way was everything. The whole universe. The entire collection of stars.

That changed only about 100 years ago.

A scientist named Edwin Hubble looked through a powerful telescope and saw something that changed everything: more galaxies. Not one. Not two. Millions. Each one a massive collection of stars just like ours. Each one far, far away. Some are shaped like saucers. Some like balls. Some are just a mess. But each one is its own galactic world.

You might be wondering—how many galaxies are there in the universe?

The truth? We don’t know the exact number. But scientists estimate there could be over two trillion. That’s a 2 followed by twelve zeroes. It’s more than the number of grains of sand on some beaches. And every single one of those galaxies holds millions or billions of stars.

Let’s pause here for a second. Not because the information is hard, but because it’s big. Enormous, even. If each galaxy has billions of stars, and there are trillions of galaxies, that means there are more stars than we could ever count. And tucked among those stars are planets—some like Earth, many not. When you look at the night sky, you're seeing just the tiniest peek into all of that.

But what makes galaxies stay together instead of just floating apart into space? One word: gravity.

Gravity is the force that pulls things toward each other. It’s what keeps your feet on the ground. It’s what makes apples fall from trees. And it’s what keeps stars, planets, and space dust orbiting inside a galaxy instead of flying away. The bigger the object, the stronger its gravity. Galaxies are held together by their own gravity. And often, there's something super powerful right at the center helping to keep everything in motion.

Want to guess what that something might be?

A black hole.

Yes, many galaxies—including our own—have a supermassive black hole in the middle. That doesn’t mean it’s sucking everything in like a space vacuum. It’s more like the engine of the galaxy. It’s powerful, massive, and plays a role in keeping the stars swirling in place. We’ll talk more about black holes later on. For now, just know that they’re part of the story.

Even though galaxies are massive, they can still move through space. They drift, spin, and sometimes crash into each other. That’s right—galaxies can collide. When they do, it’s not like cars crashing. Space is so big and stars are so far apart that most of them don’t hit each other. Instead, the galaxies mix together, stretch out, and sometimes form a new shape altogether.

Galaxies are more than just objects in space. They're clues. They tell us about how the universe works, how it grew, and maybe even how it began. By studying them, scientists learn more about the past—and maybe even about the future.

Why is it called the Milky Way?

If you were standing outside on a clear, dark night a few thousand years ago, far away from city lights or glowing screens, you would have seen something stretched across the sky that looked like a glowing band of cloud. It wasn’t the kind of cloud that brings rain or blocks the sun. It was made of light—but not just one light. It was made of the light from millions and millions of stars, all packed so closely together that they blended into a misty, glowing path. People noticed it everywhere—in every part of the world where the sky was dark enough to see it. And a lot of them gave it a name that had something to do with milk.

In ancient times, people didn’t know what galaxies were. They didn’t know stars could be clustered together like that, or that they were looking at their own galaxy from the inside. They just saw this wide stripe of brightness stretching across the sky. In many places, it reminded people of something spilled or splashed. Something soft and pale. Something smooth and white. Something like milk.

That’s where the name “Milky Way” comes from. It started with people using what they knew to describe what they saw. To early sky watchers, it looked like milk had been poured or smeared across the heavens.

The name goes way back—thousands of years. In ancient Greece, people told stories about the gods. One of them involved the goddess Hera, who was feeding baby Heracles (you might know him as Hercules). According to the myth, when Hera pulled away, milk sprayed across the sky—and that streak became the Milky Way. In fact, the Greek word for milk is “galaxias.” That’s why we use the word “galaxy” today—it came from the same root. The Romans picked up the idea, too. They called it “via lactea,” which means “road of milk.” That’s where the English name comes from.

But it wasn’t just Greek and Roman cultures that noticed the stripe in the sky. In other parts of the world, people saw it differently but still gave it names that showed how important it was. In China, it was called the “Silver River.” In parts of Africa, it was sometimes thought to be a path made by animals or spirits. In Australia, Aboriginal groups told stories that involved great rivers of light flowing across the sky. Some said it was the smoke from campfires of ancient ancestors. In Finland, it was once called “The Pathway of Birds,” because people noticed that birds seemed to follow its direction during migration.

All of these names—milk, silver, rivers, paths—point to how humans everywhere have tried to explain what they saw. Even before they understood what it really was, they knew it was something special. Something huge. Something worth naming.

Today, we know more. We know that glowing band is the view of our own galaxy, seen from inside it. We’re looking edge-on into the flat, spiral-shaped disk of stars, gas, and dust. But if you didn’t know that, and you saw it just with your eyes, what would you think? It wouldn’t look like a spiral. It wouldn’t look like a map of stars. It would still look like a stripe of light stretching across the sky. That’s what people saw for thousands of years. And that’s why the old names stuck around.

Even scientists still use the name “Milky Way.” It might sound poetic or old-fashioned, but it’s the official name of our galaxy. You’ll find it in textbooks, science articles, even space mission names. And now, we can see it in all kinds of light—not just with our eyes, but in radio waves, infrared, X-rays, and more. Each kind of light shows us a different side of the galaxy. But all of it is part of the same thing: the place we call home.

The cool thing about the name is that it shows how science and stories can live together. Long ago, people didn’t have telescopes or physics equations, but they still paid attention. They still looked up. They gave names based on what they felt, what they knew, and what they believed. Now we can measure the galaxy’s size, count its stars, and study how it spins—but we still call it the Milky Way.

That mix of old and new is part of what makes space science fun. Every discovery is built on the people who came before, even if their ideas were different. Today’s scientists are still explorers. They’re just using satellites instead of star charts drawn by hand.

When you say “Milky Way,” you’re using a name that’s traveled across centuries and cultures. You’re connecting with ancient myths and modern science all at once. And that’s kind of amazing.

Names matter. They help us talk about things. They help us connect ideas. They remind us that even something as vast as a galaxy can still feel close—like a river, a road, a ribbon of milk. Even though we know more now, the old names still help us tell the story.