What is pp cycle?

Answer 1

The pp cycle, also known as the proton-proton cycle essentially the fusion of protons into Helium 4, releasing energy in the process that fuels the stars and keeps them from collapsing under their own gravity. The p-p 1 cycle begins when two protons, under the high heat of a star's interior, are able to join together by a mechanism of quantum tunnelling. Unfortunately, this double proton nucleus is highly unstable. Luckily, via the weak force, one of the 3 quarks that make up a proton changes into another type of quark, resulting in the turning of that proton into a neutron while releasing a positron and an electron neutrino. The result is an atom of Deuterium. This atom then fuses with another proton, creating a helium 3 atom. Two helium atoms can then combine to form a helium 4 atom and 2 protons ending the p-p 1 cycle. The p-p II and p-p III cycles both begin with a helium 4 atom. p-p II begins when a helium 4 atom fuses with a helium 3 atom, resulting in an atom of beryilum 7. Beryilium 7 can then join with an electron to form Li 7, which then combines with another proton to form Beryilium 8. THis atom quickly decomposes into 2 He 4 atoms, signalling the end of the p-p III cycle. The P-P II cycle occurs wirh Beryilium 7 combines with a proton, instead of an electron, forming boron 8, which quickly decomposes into Beryilium 8, and then into 2 He 4 atoms.