Question

what is the HR path a 9-10 solar mass star takes when it dies

Answer 1

High-mass stars, like all stars, leave the Main Sequence when there is no more hydrogen fuel in their cores. The first few events are similar to those in lower-mass stars – first a hydrogen shell, then a core burning helium to carbon, surrounded by helium- and hydrogen-burning shell.Stars with masses more than 2.5 solar masses do not experience a helium flash – helium burning starts gradually.A star of more than 8 solar masses can fuse elements far beyond carbon in its core, leading to a very different fate. Its path across the H-R diagram is essentially a straight line – it stays as just about the same luminosity as it cools off. Eventually the star dies in a violent explosion called a supernova.A supernova is a one-time event – once it happens, there is little or nothing left of the progenitor star. There are two different types of supernovae, both equally common: Type I, which is a carbon-detonation supernova; Type II, which is the death of a high-mass star.Carbon-detonation supernova: white dwarf that has accumulated too much mass from binary companion If the white dwarf’s mass exceeds 1.4 solar masses, electron degeneracy can no longer keep the core from collapsing. Carbon fusion begins throughout the star almost simultaneously, resulting in a carbon explosion. i.e.  Massive stars become hot enough to fuse carbon, then heavier elements all the way to iron. At the end, the core collapses and rebounds as a Type II supernova. so final state for 9-10 solar mass is neon oxygen white dwarf