A supernova is a powerful explosion of a star when it dies. The star uses hydrogen in it’s core and turns it into helium. As this happens, it uses up the energy in it’s core, so the star starts to fade. If a star is big enough, the star can cause a supernova which happens when a star explodes and releases light, heat, and energy into space!! That heat can be 10,000 times hotter than the surface of the Sun in the Solar System!