Out in the depths of space, there’s something pulling. Galaxies far away feel the tug. Stars circle it. Closer in, long spirals of bright gas and dust swirl like water around a drain. And in the very center? Nothing. A perfect, pitchy black, sucking in everything around it.

Not a Hole

Congratulations! You’ve found one of the strangest objects in the universe—a black hole. But it’s not a hole. In fact, it’s sort of the opposite.

Black holes are real, solid objects that move around space just like stars and galaxies. In fact, some used to be stars and galaxies. But in a black hole, all the matter that used to be spread out across millions of miles is packed into a tiny space.

If a star collapses into a black hole, it will still have the same mass, and gravity—planets far away would still feel the same pull.

But close to a black hole, the gravity is intense. Gravity gets stronger the closer you are to something—and if an object is small, you can get pretty close. If you get too close to a black hole, the pull is so strong that nothing, not even light, can go fast enough to escape. Since no light escapes, they are completely dark.

So how do astronomers find them? They look for stars orbiting something with strong gravity that can’t be seen. They can also see the bright swirl of stars and gas being pulled in.

What Makes Black Holes?

Black holes are made by the same force that keeps you from floating off Earth—gravity. Gravity pulls all matter together. The more mass (stuff, atoms) in an object, the stronger its gravity

Even tiny molecules of gas out in space have (very tiny) gravity. As clouds of gas swirl around, the gravity of all the little particles tugs them together into lumps. That’s how stars and planets form.

But sometimes, when enough matter clumps together in one place—say, in a supermassive star—things can get weird. When the star runs out of fuel, its own gravity can collapse its atoms into a dense paste. It’s like crushing a Styrofoam cup—the more you crush, the smaller it gets, even though all the Styrofoam is still there.

At some point, the star gets so dense that gravity just wins. The star collapses into a single point, infinitely small and infinitely dense. This mysterious object is called a singularity. It’s the heart of a black hole. No one really knows what a singularity looks like, and no one ever will. That’s because nothing escapes from a black hole—not even light.

Light is the fastest thing in the universe. But it does follow curves in space. And a black hole’s gravity bends space around it in a kind of infinite cone. So light can go in, but it can’t get out.

Anything else that falls in can’t get out, either. Stars, planets, dust—anything that passes the edge gets gobbled up. This means black holes keep growing. The more stuff goes in, the bigger it gets.

The black disk of a black hole is actually a dark boundary called the event horizon. Past this edge, gravity traps light. If you’re farther away than that, you might be able to pull free, if your engine is strong enough. But past the horizon, it’s like falling over a waterfall. There’s no way back out.

Falling In

What would happen if you fell into a black hole?

For starters, you’d have to go a LONG way to find one. There are many black holes in the universe. There’s probably one in the center of most galaxies. But the closest one to Earth would take a spaceship millions of years to reach.

The closer you get to a black hole, the more strongly it would pull you. But in your spaceship, you would not feel anything odd. That’s because you and the ship would both be zipping toward the black hole at the same speed. You might not even notice!

But as you got close to the event horizon, things would get weird.

Black holes bend space around them, which also slows time. For you, time would seem to move normally. Stars would seem to smear out, then go dark. But to any pals watching from far away, your spaceship would seem to go slower and slower, and then stop, as if it were hanging just at the edge of the black hole.

As you pass the event horizon, you might get stretched out thin, like a piece of spaghetti, before slipping inside. After that, the intense gravity would smoosh your atoms into some weird quantum mush, like everything else inside.

But that doesn’t mean nothing escapes from a black hole. In fact, over a long time, they might even evaporate! How?

Empty space is never really empty. All over space, tiny pairs of particles and anti-particles are constantly popping in and out of existence. Every once in a while, near a black hole, one will fall in, while the other escapes. That escaping particle steals a bit of mass from the black hole. It may take billions of years, but eventually, the black hole can entirely disappear this way. This weird possibility was thought up by the famous astrophysicist Stephen Hawking, and it’s called Hawking radiation.