Supernovas are a natural phenomenon that occurs in space with some regularity for it lies in the natural cycle of a star's life. Every star that is formed, if large enough, will induce a supernova upon its demise. They are powerful events capable of releasing extensive amounts of radiation into the cosmos. If one would have occurred in some proximity to Earth, it would inevitably destroy life on our planet. This is the basis of the Supernova Theory. It has been suggested that Cretaceous life was ended by comic radiation from a nearby supernova explosion.

If a supernova occurred near Earth, the radiation from it would destroy our ozone layer and taint our atmosphere. If the ozone is obliterated, then there is no barrier left for the prevention of other cosmic radiation to affect life. Life as we know it would end. This type of event would have definitely have the devastating effects necessary to cause a mass extinction.

Also, a supernova would explain the presence of Ir at the K/T boundary. When a star undergoes a supernova, heavier elements are created by the process; these elements are then radiated out into the solar system by the following explosion of the star. The heavier elements created can include Ir. So if a supernova did indeed end life 65Ma ago, then the presence of Ir at the boundary is perfectly justified.