(15) The second step of the proton-proton cycle involves the fusion of a proton with a deuteron (formed in the first step). Given that only one of the products of the fusion has any mass or charge, describe the product. What other products could be created in this step?
The product must have atomic mass of approximately 3 amu and charge +2. In terms of nuclear particles, the product consists of 2 protons and 1 neutron. Other products of this reaction would have to be mass less and change less. One particle with these qualities is the photon. In this case, however, the mass less, change less particle is a neutrino, or small neutron. Like a neutron, it has no charge. However, its mass is insignificant even compared to the mass of an electron. The actual reaction is
