Transcript: Mass extinctions cannot only be caused by impacts from space or by violent geological change. They can also potentially be caused by the death of stars. Supernova represents the death of a massive star, leaving a compact remnant of a neutron star or black hole. When a supernova goes off, there is a huge amount of light emitted, also a large amount of high energy particles or cosmic rays. The incidence rate of supernova is very low, only one in the entire Milky Way galaxy every hundred years. It’s been four hundred years since humans witnessed supernovae, and the nearest versions four hundred years ago were several hundred lightyears away. If however, a massive star went off or died within ten or twenty lightyears of the Earth, it would release a flood of cosmic rays that would cause a spike in the mutation rate of species and probably could lead to a mass extinction. We don't know when or if such an event happened, but statistically it is likely that over the history of life on Earth, several times, dying stars have gone off within a few lightyears of the Sun.