Stars generate the energy that makes them shine as a by-product of nuclear fusion and not by shrinking, as scientists had once believed. A. The Sun is a good example of a Population I star because the Sun generates its energy through nuclear fusion rather than through contraction. B. In the Milky Way, Population I stars are found in and around the central bulge and Population II stars are found in the galactic disk. C. The Sun and stars like it will separate into inner cores and outer envelopes before all nuclear reactions in the cores stop and the stars finally die. D. Population II stars, the oldest stars, are formed from hydrogen and helium gases, and they shine until they exhaust their fusible material. E. Population I stars, including the Sun, are relatively young stars that are mostly hydrogen and helium gas but also contain heavier elements. F. The outer envelope of the Sun and stars like it will release their energy into space, and the inner cores will become white dwarfs before they finally give off their last energy.