A core collapse supernova (Type II supernova, CCSN) is a supernova caused by the collapse of a stellar core. They are identified by hydrogen spectral lines and occur in the post-main-sequence stage of early stars above about 8 solar masses (core collapse progenitors), but above some mass around 40 to 50 solar masses, they are expected to collapse without the vast optical output of a supernova. They are generally observed in HII regions and spiral arms (such massive stars are expected to have short lives, thus end their life within regions of recent star formation). Some core collapse supernovae emit radio and are termed radio supernovae (RSNe). The radio is sufficiently weak that it is currently detected only from limited distances and few have been observed.
Type Ib supernovae and Type Ic supernovae are presumed to be core collapse supernovae of stars missing some of their outer shells/envelopes, thus lacking some emission lines they would otherwise have. A Type Ic supernova has lost much of its hydrogen envelope and a Type Ib supernova, all of it. These are termed stripped supernovae or stripped-envelope supernovae, the term ultra-stripped supernova (USSN) indicating an extreme case.
A fallback supernova is a supernova (typically core collapse) which leaves some of the expelled material gravitationally bound, to be subsequently accreted. This is theorized to be the cause of some observed light curves over the first few weeks.
An electron capture supernova is a core collapse supernova in which the core collapse is triggered by electron capture by magnesium and neon: experiment and analysis has indicated it can result in a supernova explosion lacking the fusion of a Type Ia supernova and can produce a neutron star (NS).
In some cases, a pulsar which is apparently the remnant left by the supernova is moving away from the location, possibly the result of an anisotropic explosion pushing it away (a kick), the push termed a pulsar kick (or neutron star kick or NS kick).
As of 2017, core collapse supernovae have yet to be convincingly simulated: if sufficiently large and fuel-depleted, a simulated star has collapsed into a stellar remnant, but the simultaneous generation of an explosion large enough to qualify as a supernova (on the order of 1 foe) apparently depends on exotic processes, apparently requiring advances in simulations. Processes include neutrino interactions, and perhaps general relativity. Simulation trials suggest that a core collapse does not always cause a supernova, even within the specified mass range, but also depends on convection, turbulence, rotation, and/or magnetism.