carbon-nitrogen cycle n.
A chain of thermonuclear reactions in which nitrogen isotopes are formed in intermediate stages and carbon acts essentially as a catalyst to convert four hydrogen atoms into one helium atom with the emission of two positrons. The entire sequence is thought to generate significant amounts of energy in the sun and certain other stars. Also called carbon cycle, nitrogen cycle.
See carbon cycle.
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sequence of thermonuclear reactions that provides most of the energy radiated by the hotter stars. It is only a minor source of energy for the Sun and does not operate at all in very cool stars. Four hydrogen nuclei are in effect converted into one helium nucleus, a fraction of the mass being released as energy (according to the law of mass-energy equivalence, E = mc2). The German-U.S. physicist Hans Bethe, in 1938, first described the process.
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