Abstract :
Low-mass metal-poor stars were formed at early times when only a small number of massive stars had had time to evolve and chemically enrich the universe. Therefore, the observed elemental abundances in these metal-poor stars are fossil records of the nucleosynthetic contributions of massive stellar sources. Based on these observations, it is argued that there must be three distinct sources for the elements from Na to U in the early universe, and these are low-mass supernovae, normal supernovae, and hypernovae associated with massive stars of ~8–11 M⊙, ~12–25 M⊙, and >25 M⊙, respectively.
