Hi Canyon, The Sun is about 4.6 BILLION years old. Astronomers believe that the Sun will live to about 10 billion years old, so it has only lived about half of its life. However, just like us, different kind of stars live for different lengths of time. Bigger, hotter stars tend to use up all of their energy much faster and die younger, while smaller cooler stars live longer. Also the stars go through different phases throughout there lifetime. Astronomers use diagrams called Hertzsprung-Russell diagrams to look at how a star changes as it gets older. There is a good example here: http://www.daviddarling.info/images/Hertzsprung-Russell_diagram.jpg Each colored dot is a star and they are ordered by their temperature and their Luminosity (basically how much energy they emit i.e. how bright they are). Stars to the left are hottest and the ones on the right are cooler. The higher up the graph you go the brighter the star is. The stars at the top left are the big hot stars that die young. And the bottom right are the smaller, cooler stars that live longer. The diagonal stripe through the middle of the diagram is called the Main Sequence. Our Sun is on there, can you find it? That's where the stars spend most of their life and during that time they burn Hydrogen. Once they use up all of their Hydrogen they start to burn Helium and they move over to the Giants and Supergiants. When our Sun is much older it will become a red giant. When this happens the Sun will get much bigger and will expand out to about the orbit of the Earth, swallowing up Mercury and Venus. But don't worry, this won't happen for about another 5 billion years! Hazel