Our sun is a star ,and nine words move round it .Words like these are planets (行星).
But there are other stars ,other suns ,not only thousands of them ,but millions of them .Do you different stars have planets ?We can see the planets round our own sun .But we haven*t seen anymore .The stars are too far away from us .Stars give out (发出)light ,but the planets don*t have any light of their own .So we can*t see them .They are 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（巴纳德星）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 known Barnard*s Star for many years ,and now we are sure it has a planet.