Galaxy

A galaxy is like a super-duper big city made of stars! It also has gas and dust, all held together by something called gravity. Our own Sun lives in a galaxy called the Milky Way.

Most galaxies are so huge they have about 100 million stars, but some are tiny with just a few hundred, and others are ginormous with a trillion stars! That's more stars than grains of sand on all the beaches in the world!

Galaxies are mostly made of invisible stuff called dark matter. We can't see it, but it's like the glue holding everything together. The stars and colorful gas clouds we can see are only a tiny part of a galaxy.

At the very center of most galaxies, there's a super-powered black hole, which is so strong it pulls everything towards it. It's like a giant vacuum cleaner in the middle of the star city!

Scientists think there are billions and billions of galaxies in the universe, maybe even two trillion! That's more than you can count in your whole life. Some galaxies look like spinning pinwheels, called spiral galaxies.

Others are round and smooth like a fuzzy ball, called elliptical galaxies. And some are just messy shapes, called irregular galaxies. Our Milky Way is a spiral galaxy, with long arms reaching out.

Galaxies are incredibly far apart. The space between them is almost empty, with hardly any gas. Our Milky Way galaxy is about 87,400 light-years across. A light-year is the distance light travels in one year, and light is super fast! The closest big galaxy to us is Andromeda, and it's still over 2.5 million light-years away. That's a really, really long trip!