The story of the wise men from the East is only in the Gospel of Matthew. Why is it only in this gospel, and what is its meaning?
Jesus is the messiah for all the nations. Matthew, a gospel written originally for the Jews, includes the story of the wise men, gentiles, to make clear that Jesus is for all the world, not just Israel.
God can use anything and everything to proclaim the good news of Jesus -- the stars, the universe, all of nature. We, like the wise men, are gentiles who came to Christ. Now, we need to be like the star itself, leading people to Him. We, as people, can do more than the star: we can go to people and tell them about Christ.