What is the proton-proton chain?

Answer 1

Well, there are 4 branches of the Proton-proton chain. But over all in this reaction, 4 Hydrogen's (protons) are turned into a helium atom (2 protons and 2 Neutrons)

pp Branch I:

Two protons collide, one of the protons turn into a neutron, this releases a positron and a neutrino. The result is a Deuterium, which is just 1 proton and 1 neutron bound together. The the positron that was released by this reaction almost immediately annihilates with an electron, giving of 2 gamma rays. The Neutrino escapes the star, carrying away some energy.

Next, the Deuterium collided with another proton, so now we have 2 protons and 1 neutron bound together, this is a Helium-3 isotope. This reaction releases a gamma ray.

The Helium-3 will now collide with another Helium-3 (a total of 4 protons and 2 Neutrons), 2 of the protons are released to start the whole process over again, so your left with a regular Helium atom (2 protons and 2 Neutrons).

This branch of the PP chain happens most frequently in the sun, about 86% of the time. This branch works best at 10-14 million K.

pp Branch II:

This branch happens only about 14% of the time.

In this branch, when the Helium-3 is made, instead of combining with another Helium-3, its combines with a previously formed Helium atom, to make a Beryllium-7 (4 Protons, 3 Neutrons), this releases a gamma ray.

The Beryllium-7 now captures and electron, the Electron fuses with one of the Protons in the Beryllium-7 to make a neutron, so now we have a Lithium-7 (3 protons, 4 Neutrons), and a neutrino is released.

The Lithium-7 then collided with another proton, giving a total of 4 Protons and 4 Neutrons, which is 2 Helium atoms.

This branch is most dominant at 14-23 million K.

pp Branch III:

This branch is very rare, only happens .11% of the time. And it is most dominant at temperature exceeding 23 million Kelvin.

In the Branch, the Helium-3 combines with a previously formed Helium atom, and just like in pp Branch II, this produces a Beryllium-7, releasing s gamma ray.

Now this Beryllium-7 collides with another proton, making a Boron-8 (5 Protons, 3 Neutrons), this also releases a gamma ray.

On the Protons in Boron-8 will now turn into a neutron, giving a total of 4 Proton and 4 Neutron, which is 2 Helium atoms.

Once the Proton convert to a neutron, it releases a positron, a Neutrino and another gamma ray.