A supernova is a powerful and luminous stellar explosion. This transient astronomical event occurs during the last evolutionary stages of a massive star or when a white dwarf is triggered into runaway nuclear fusion. A supernova is a spectacular explosion of a massive star. If our sun exploded as a supernova, the resulting shock wave probably wouldn't incinerate the entire Earth, but the side of Earth facing the sun would boil away. A previous study found that any supernova that went off within about 25 light-years would be enough to wipe us out, but any farther than that and we'd be mostly safe. New research, however, increases that "kill zone" to 50 light-years. When the pressure drops low enough in a massive star, gravity suddenly takes over and the star collapses in just seconds. This collapse produces the explosion we call a supernova. Supernovae are so powerful they create new atomic nuclei. Our sun is too small to go nova or supernova. It will ultimately enter a red giant stage and then collapse as a white dwarf. It would need to be at least eight times more massive to nova. Scientists have discovered what appears to be a rare cosmic event where a black hole has consumed a star from inside out, resulting in a massive supernova. Stellar-mass black holes are born with a bang. They form when a very massive star (at least 25 times heavier than our Sun) runs out of nuclear fuel. The star then explodes as a supernova. The events at the end of a star's life depend on its mass. Really massive stars use up their hydrogen fuel quickly, but are hot enough to fuse heavier elements such as helium and carbon. Once there is no fuel left, the star collapses and the outer layers explode as a 'supernova'. Supernovae may be divided into two broad classes, Type I and Type II, according to the way in which they detonate. Type I supernovae may be up to three times brighter than Type II; they also differ from Type II supernovae in that their spectra contain no hydrogen lines and they expand about twice as rapidly. A Type Ia supernova is a type of supernova that occurs in binary systems in which one of the stars is a white dwarf. The other star can be anything from a giant star to an even smaller white dwarf. Physically, carbon–oxygen white dwarfs with a low rate of rotation are limited to below 1.44 solar masses. A star can go supernova in one of two ways: Type I supernova: star accumulates matter from a nearby neighbor until a runaway nuclear reaction ignites. Type II supernova: star runs out of nuclear fuel and collapses under its own gravity.

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