Nova

A nova is an astronomical event that creates a bright "new" star that slowly fades over several weeks. They are created in a close binary star system consisting of a white dwarf and either a main sequence, subgiant, or red giant star. When the white dwarf is close enough to its companion star, it is thermally heated by the hot white dwarf and this eventually causes rapid runaway fusion and the death of the progenitor star. This is seen as visible light during the nova event and used to be mistaken as a "new" star.