Spiral arm

Okay kiddo, you know how some galaxies look like big, bright circles in the sky? Well, some of those galaxies have arms that spiral out from the center. Imagine a whirlpool in a bathtub - the water swirls around and around, just like the stars in a spiral galaxy. These arms are made up of millions of stars and gas clouds that all move together in a spiral shape. Scientists are still trying to figure out why these arms form, but they think it might have to do with gravity pulling everything towards the center of the galaxy. So remember, a spiral arm is like a swirling pattern of stars in a galaxy that looks kind of like a giant whirlpool!