In a binary-star system that produces a nova, the white dwarf pulls matter from the companion star. the matter forms an accretion disk that orbits the white dwarf. then a specific sequence of events must take place for a nova event to occur.1. Material accumulates onto the white dwarf's surface, increasing in temperature and density. 2. At a temperature of 10 million K, the accumulated surface hydrogen begins nuclear fusion. 3. Nuclear fusion reactions cause an enormous but temporary increase in luminosity. 4. As nuclear fuel is burned up or blown into space, fusion ceases and the star dims.