This work is intended to develop a new direction of theoretical and nuclear astrophysics by studying reactions that occur at high pressure on the crusts of neutron star. Interest in neutron stars is related to the mystery of its structure. In addition, there are a high density, an extremely strong magnetic and gravitational fields. The physical properties of leptons in weak interaction are involved and provided. The manifestation of lepton universality is discussed. The decay of the muon was investigated in the standard model. The ways in which muons occur in denser matter are studied. The muon is a very unstable particle on Earth. Its lifetime is a few microseconds. However, in a very dense, neutron star, it is stable. The appearance of muons in the composition of denser stars, that is, the transformation of the electron into a muon is energetically advantageous. It can also participate in some nuclear reactions.