3. KEY differences Type 1: The explosion results from sudden fusion on its surface. Type 2: The explosion results from collapse of the core. Type 1: The star is totally destroyed. Type 2: The core remains intact as a black hole or neutron star. Type 1: The mass and brightness is very consistent for each one. Type 2: The mass and brightness vary over a wide range. Type 1: Needs to be within the Roche lobe of a red giant star. Type 2: Needs to be above about 3 solar masses. Type 1: Occurs in a stellar remnant (white dwarf). Type 2: Occurs in a giant star just after the main sequence but prior to becoming a stellar remnant.