How does a Star die?

Stars die when they eventually use up all their fuel and burn out, but this process takes many millions of years. Towards the end of its life, a star starts to run out of hydrogen to power its nuclear fusion. It starts to cool, becoming a red giant. The red giant swells, and the pressure at its centre becomes so great that the star begins absorb energy instead of emitting it. In a matter of seconds the star collapses, then explodes into a supernova. This is a huge explosion of light and energy that can be seen right across the galaxy.