Fusion and Dissociation of Nuclei in First & Second Generation Stars


Figure 7.  Nuclear evolution in the Sun and in first generation stars, illustrated on a plot of M/A vs. 1/A.  1.  First generation stars fuse 1H into heavier nuclides.  2.  At the end of their life, material in the core may be compressed into a neutron star (NS).  Our Sun, a second generation star, formed on this product.        3.  The NS acts as a giant nucleus, decaying with the emission of neutrons (Q = 10-22 Mev/neutron; t1/2 approximately equals 1010 years).                            4.  Neutrons and their decay product, 1H, are mostly consumed by fusion as they migrate upward, carrying lighter elements and the lighter isotopes of each element to the solar surface.  This fusion repeats step 1.