Example of our chemically homogeneous evolution model, with initial parameters indicated by text. The left panel presents the evolution of the chemically homogeneously evolving star on the Hertzsprung–Russell diagram, where the square and diamond mark helium ignition and the middle of helium burning. The right panel shows the chemical evolution of the chemically homogeneously evolving star as a function of its age. The blue, orange, and green correspond to the evolution of core helium, surface hydrogen, and core hydrogen.