When the progenitor star is below about – depending on the strength of the explosion and the amount of material that falls back – the degenerate remnant of a core collapse is a neutron star. Above this mass, the remnant collapses to form a black hole. The theoretical limiting mass for this type of core collapse scenario is about . Above that mass, a star is believed to collapse directly into a black hole without forming a supernova explosion, although uncertainties in models of supernova collapse make calculation of these limits uncertain.