Dark matter halo

Okay, so imagine you have a big ball, like a soccer ball. Now, throw that ball up into the air. What happens? It falls back down, right? That's because of a force called gravity. Gravity is what makes things fall back down to Earth instead of floating away into space.

Now, scientists have been studying gravity for a long time, and they've noticed something kind of strange. When they look at the way galaxies (which are like big groups of stars) are moving, they see that they're moving differently than they should be based on the amount of gravity we can see. It's like there's more gravity there than we can account for. This extra gravity is what we call "dark matter."

So, a dark matter halo is kind of like an invisible "cloud" of dark matter that surrounds a galaxy. It's called a "halo" because it looks like it's surrounding the galaxy like a halo on a person's head. Scientists can't see or directly observe dark matter, but they can tell it's there because of the way it affects the movement of stars and other objects in the galaxy.

So, think of it like this: imagine you're playing a game of tag, and there's someone hiding behind a tree. You can't see them, but you can tell they're there because you can hear them breathing and you can feel the wind they create when they move around. Dark matter is kind of like that hidden player in the game of tag – we can't see them, but we can see the effects they have on the game.