Why are there three stars in the night sky always in a straight line?

Now there are three stars in a straight line near the zenith, namely Betelgeuse, Betelgeuse and Akisaka of Orion. These three stars are Orion's belt. This constellation is the first one I know. Orion has many bright stars. Among them, Betelgeuse and Betelgeuse are two bright stars, which are one of 2 1 star except the sun that we see on the earth. The former ranks 12, while the latter ranks 7. It is also easy to know by these two bright stars. Orion is now visible in the east around 20 pm, and will move towards the zenith more and more as time goes by. The following are

I hope it helps you.