Astronomers are scrutinizing a star system in a distant galaxy that exploded, possibly leaving behind a zombie star. They say their study of this system will help them understand supernova explosions, which are an important piece of the cosmic puzzle, used to help measure distances in vast space and the expansion of the universe. Standard Type Ia supernovae occur when a white dwarf draws enough material from a companion star onto itself to raise its own core temperature, ultimately creating a runaway nuclear reaction that causes the white dwarf to explode as a supernova. In such cases, the explosion typically...