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Eight, the energy of the star
Stars have two most important characteristics. The first feature is that it has a huge mass, and the gravity generated by the mass makes the star material converge toward the center. The second characteristic is that there is a strong thermonuclear reaction, mainly the thermonuclear reaction in which hydrogen atoms fuse into helium nuclei. The pressure generated by thermonuclear reaction causes the stellar matter to spread outward. Only when gravity and pressure are balanced can a star remain stable (Figure 5. 1. 1). Proton-proton reaction and carbon cycle are both reactions in which hydrogen nuclei coalesce into helium nuclei, and both reactions will occur in stars. Inside the sun, 99% of energy comes from proton-proton reaction, and 1% comes from carbon cycle.
The solution of the problem of stellar energy mechanism makes human realize that there is huge energy in the nucleus, which opens a new era for human to develop nuclear energy. Manhattan Project (the project of Americans secretly developing atomic bombs) used nuclear energy to make new weapons in World War II and put them into practice. The construction of nuclear power plants provides mankind with more efficient energy. The manufacture of hydrogen bomb is the direct application of thermonuclear reaction of hydrogen fusion to helium nucleus.
Internal pressure diagram of stars