The collapse of a massive non-degenerate core will ignite further fusion. When the core collapse is initiated by pair instability (photons turning into electron - positron pairs, thereby reducing the radiation pressure) oxygen fusion begins and the collapse may be halted. For core masses of 40–60 M ☉, the collapse halts and the star remains intact, but collapse will occur again when a larger core has formed. For cores of around 60–130 M ☉, the fusion of oxygen and heavier elements is so energetic that the entire star is disrupted, causing a supernova. At the upper end of the mass range, the supernova is unusually luminous and extremely long-lived due to many solar masses of ejected Ni. For even larger core masses, the core temperature becomes high enough to allow photodisintegration and the core collapses completely into a black hole.