Hello. There are so many answers to this question,that only lead to more questions. first off the universe is continuously expanding, and has been for the past 14 billion years, this is a result of the big bang theory, the beginning of time for the existence of our universe. as the universe began to cool small groups of stars began to come together to create galaxies like our milky way. with in our galaxy, our star was born, and as it grew more powerful it began to pull objects in around it with its gravitational pull. these objects became our solor system.