91Ó°ÊÓ

One of two known sets of nuclear fusion events by which stars convert hydrogen to helium is the proton–proton chain, often known as the\({\rm{p - p}}\)chain. It is dominant in stars with masses less than or equal to that of the Sun, but theoretical models imply that the\({\rm{CNO}}\)cycle, the second known reaction, is dominant in stars with masses more than around\({\rm{1}}{\rm{.3}}\)times that of the Sun.

The following is the reaction –

\({\rm{2}}{{\rm{e}}^{\rm{ - }}}{\rm{ + }}{{\rm{4}}^{\rm{1}}}{\rm{H}}{ \to ^{\rm{4}}}{\rm{He + 2}}{{\rm{\nu }}_{\rm{e}}}{\rm{ + 6}}\gamma \)

Analyse the number of charges, nucleons, and family for each constituent –

Conservations:

• Charge - Before \( - 2 + 4 = 2\), after only helium (two protons, two neutrons) is obtained, so now it is \(2 - 2\) which is conserved.
• Nucleons - Before \({\rm{41}}\) (hydrogen), helium has four nucleons (two protons, two neutrons), \(4 = 4\), which is conserved.
• Lepton family - Electron and their neutrinos are having positive lepton family number. With two electrons on the left and two-electron neutrinos on the right, it is \(2 - 2\), which means the lepton family number is conserved.

Therefore, all the quantities are conserved.