The Sun is going out!
So as with everything else in the
world galaxy, the gases in the Sun are a non-renewable resource. Apparently our poor sun is burning itself out and will come to a final fade in about 5 Billion years. Better hurry outside and get your tan on!
Seriously though, apparently after 5B years, it will swell into a giant red star. It should last for about 10,000 years in a nebulous state before it goes out with a bang. There's a kewl new book by astronomy journalist Stuart Clark that describes this process and showcases some incredible images of nebulae. You can view an online Image Gallery of these images. Take a look. They are really breathtaking.
Source: New Scientist