where does hydrogen fusion begin?

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  • 1 decade ago
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    The fusion of hydrogen into helium releases huge amounts of energy and is the main energy source of stars, including the sun.

    The proton-proton chain reaction is one of several fusion reactions by which stars convert hydrogen to helium, the primary alternative being the CNO cycle. The proton-proton chain dominates in stars the size of the Sun or smaller.

    Overcoming electrostatic repulsion between two hydrogen nuclei requires a large amount of energy, and this reaction takes an average of 109 years to complete at the temperature of the Sun's core. Because of the slowness of this reaction the Sun is still shining; if it were faster, the Sun would have exhausted its hydrogen long ago.

    In general, proton-proton fusion can occur only if the temperature (i.e. kinetic energy) of the protons is high enough to overcome their mutual Coulomb repulsion. The theory that proton-proton reactions were the basic principle by which the Sun and other stars burn was advocated by Arthur Stanley Eddington in the 1920s. At the time, the temperature of the Sun was considered too low to overcome the Coulomb barrier. After the development of quantum mechanics, it was discovered that tunneling of the wavefunctions of the protons through the repulsive barrier allows for fusion at a lower temperature than the classical prediction.

  • Anonymous
    1 decade ago

    When the protostar reaches a sufficient temperature to sustain fusion. Initially fusion begins in the core of the sun, and the energy radiates outwards. The energy created in the sun takes several million years to make it's way out of the sun, and into the solar system.

  • Anonymous
    1 decade ago

    the H in hydrogen

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