Our sun is a star, and nine worlds move round it. Worlds like these are planets  . But there are other stars, other suns. Not only thousands of them, but millions of them. Do different stars have planets? We can see the planets round our own sun. But we haven't seen any more. The stars are too far away from us. Stars give out  light, but the planets don't have any light of their own. So we can't see them. They're too far, and too dark. Still, we can tell that some stars have planets. While a big planet goes round, it pulls its star to one side. And sometimes we can see this, Then we know that the star has a planet. For example, Barnard's Star is a small red star. And it is the quickest star in the universe. But sometimes it moves slower, and then quicker again. We have know Barnard's Star for many years, and now we are sure it has a planet. How can people know that there is a plante round Barnard's Star?
Sometimes they see that the planet pulls the star to one side and makes it move slower . The planet is shining. The planet is next to our earth. The planet is a red one.