The evolution and explosion of massive stars

TLDR

Massive stars are gravitationally confined thermonuclear reactors that evolve to ever higher temperatures, fuse heavier elements until an iron core forms, and whose collapse releases enough energy to trigger a supernova explosion. The study reviews the post‑helium‑burning evolution of massive stars, focusing on their nuclear and stellar physics. The authors review supernova explosion mechanisms, shock hydrodynamics, fallback, and the nucleosynthesis of heavy elements, noting that massive stars produce isotopes from mass 16 to 88 and many r‑ and p‑process elements. Model predictions of neutron star masses, supernova light curves, and spectra agree with observations.

Abstract

Like all true stars, massive stars are gravitationally confined thermonuclear reactors whose composition evolves as energy is lost to radiation and neutrinos. Unlike lower-mass stars $(M\ensuremath{\lesssim}{8M}_{\ensuremath{\bigodot}}),$ however, no point is ever reached at which a massive star can be fully supported by electron degeneracy. Instead, the center evolves to ever higher temperatures, fusing ever heavier elements until a core of iron is produced. The collapse of this iron core to a neutron star releases an enormous amount of energy, a tiny fraction of which is sufficient to explode the star as a supernova. The authors examine our current understanding of the lives and deaths of massive stars, with special attention to the relevant nuclear and stellar physics. Emphasis is placed upon their post-helium-burning evolution. Current views regarding the supernova explosion mechanism are reviewed, and the hydrodynamics of supernova shock propagation and ``fallback'' is discussed. The calculated neutron star masses, supernova light curves, and spectra from these model stars are shown to be consistent with observations. During all phases, particular attention is paid to the nucleosynthesis of heavy elements. Such stars are capable of producing, with few exceptions, the isotopes between mass 16 and 88 as well as a large fraction of still heavier elements made by the $r$ and $p$ processes.