Transcript: Consider a binary system where a giant or a supergiant star is in orbit around a white dwarf and where a mass transfer between the lobes pushes the white dwarf over the Chandrasekhar limit. At this point the white dwarf collapses catastrophically to form either a neutron star or a black hole blasting off a lot of material in a titanic explosion called a supernova. This particular type of supernova that occurs in binary systems is a Type II supernova, and because of the regulated way in which the mass is added to the white dwarf, the luminosity, which at its peak can exceed the luminosity of the entire Milky Way, is a well regulated number, a standard candle as astronomers would say. The incidence rate of supernovae is a thousand times less than the incidence rate of novae.