A big bang happened 13.8 billion years ago and that was the birth of our Universe which expanded from a dot to several billion kilometers in a few minutes! After 400 million years, the first stars and galaxies were formed. And about 4.6 billion years ago, our sun was born from the remnants of a supernova explosion of another star. and then all the planets and the solar system was formed. We also learn a lot of fun facts about the Sun.