Editing Proton–proton chain (section)

===Energy release===
Comparing the mass of the final helium-4 nucleus with the masses of the four protons reveals that 0.7 percent of the mass of the original protons has been lost. This mass has been converted into energy, in the form of kinetic energy of produced particles, gamma rays, and neutrinos released during each of the individual reactions. The total energy yield of one whole chain is {{val|26.73|u=MeV}}.

Energy released as gamma rays will interact with electrons and protons and heat the interior of the Sun. Also kinetic energy of fusion products (e.g. of the two protons and the {{nuclide|link=yes|helium|4}} from the {{nowrap|p–p I}} reaction) adds energy to the plasma in the Sun. This heating keeps the core of the Sun hot and prevents it from [[gravitational collapse|collapsing]] under its own weight as it would if the sun were to cool down.

Neutrinos do not interact significantly with matter and therefore do not heat the interior and thereby help support the Sun against gravitational collapse. Their energy is lost: the neutrinos in the {{nowrap|p–p I}}, {{nowrap|p–p II}}, and {{nowrap|p–p III}} chains carry away 2.0%, 4.0%, and 28.3% of the energy in those reactions, respectively.<ref>Claus E. Rolfs and William S. Rodney, ''Cauldrons in the Cosmos'', The University of Chicago Press, 1988, p. 354.</ref>

The following table calculates the amount of energy lost to neutrinos and the amount of "[[solar luminosity]]" coming from the three branches. "Luminosity" here means the amount of energy given off by the Sun as [[electromagnetic radiation]] rather than as neutrinos. The starting figures used are the ones mentioned higher in this article. The table concerns only the 99% of the power and neutrinos that come from the {{nowrap|p–p}} reactions, not the 1% coming from the CNO cycle.

{| class="wikitable"
|+ Luminosity production in the sun
|-
! Branch 
! Percent of<br><sup>4</sup>He produced 
! Percent loss<br>due to neutrino<br>production 
! Relative<br>amount of<br>energy lost
! Relative amount<br>of luminosity<br>produced
! Percentage<br>of total<br>luminosity
|-
| Branch I   || {{0}}83.3%      || {{0}}2%   || 1.67%   || 81.6%   || {{0}}83.6%
|-
| Branch II  || {{0}}16.68%     || {{0}}4%   || 0.67%   || 16.0%   || {{0}}16.4%
|-
| Branch III || {{0|00}}0.02% || 28.3%     || 0.0057% || {{0}}0.014% || {{0|00}}0.015%
|-
| total      || 100%       ||           || 2.34%   || 97.7%   || 100%
|}