Astronomy - The Sun (5.5 of 16) What is the Proton-Proton Chain? 

All of us 408K scientists also did the same thing!

Not sure what you meant by "the order of magnitude of around 7". The basic principle as explained in this video is correct, with the minimum temperature for nuclear fusion being about 10 million K and the central core temperature of the Sun estimated to be about 15 million K which accounts for the faster fusion process. However that said you are correct in mentioning that there additional factors to be considered. We will explain those when we cover this topic in our new astrophysics videos where we will calculate the more precise process of the nuclear fusion process.

Note that this happens when 2 protons fuse together. The mass loss of that reaction accounts for the ability to emit a positron and neutrino.

Hi. what is your major or class?

That is a very interesting way of looking at it. Thanks for sharing.

Sources: _Foundations of Astronomy,_ 8th, Seeds. Wikipedia, and many more, state 9 billion years. My textbook some years back stated 1 billion years for the first step, as quoted. _The Physics of Stars,_ Phillips.

The Sun produces about 4 x 10^26 W of power. Divide 4 x 10^26 by 25 MeV (coverted to Joules) = 1 x 10^38 reactions Therefore the Sun ejects 2 x 10^38 neutrinos per second. (Then divide by the surface area of a sphere with Earth's radius (converted to m)) And you have 2 x 10^38 / 4 x pi x (1.5 x 10^11)^2 = 350 trillion neutrinos per square meter

Sir there is cubic metre what to do with it

Thank you so much sir

Since they move at speeds close to the speed of light we can assume v = c They you have to divide that amount by c. 350 trillion / 3 x 10^8 = 1.2 x 10^6 /m^3 / sec = 1.2 million / m^3 / sec

@@MichelvanBiezen thank you sir.

Vinicius, It depends on several things. One of the important aspects is what you want to do for a job. Sometimes you need this knowledge so you can perform well on the job. But for personal satisfaction and fulfillment, we also learn to gain knowledge and understanding. I will be making a series on quantum mechanics, but that may be a while, since I am working on several other series first.

Thanks Michel for the responding me,i'm glad to know you will do one day a series about this topic, which is very complicated, and i'm studying various things to understand this, i'm only a high school student, from youtube, you are the best to explain ANYTHING!

The proton-proton chain process is the main nuclear fusion process in the Sun. There are other fusion reactions but they are not as common.

I have the same doubt miss. Temperature require to over come barrier (height for p-p fusion is 400keV ) is 3*10^9 Kelvin but sun 's interior temperature is of 1.5* 10^7K . Evidently sun's temperature is not enough to impart proton kinetic enrgy to overcome the barrier. Could you please simplify you last lines of your comment ,how does fusion takes place ? Does it has anything to do with Tunneling ?

Glad it was helpful!

There is mass loss in each step of the process.

Sorry to bother you further sir, but I'm really grateful if you could elaborate this for me, because I'm really interested on this. Pls correct me if there's misconception in my understanding, I understand there is mass loss in 1st step due to 2 protons of H fused into He with 2 protons -> one of which then converted into neutron and produces 1 positron and 1 neutrino. or in 3rd step where two He-3s fused into alpha particle He and kicks 2 protons out. but in 2nd step where the deuterium fused with normal H become He-3 does not kicking out anything, all the particles are there (2E, 2P, 1N). You did say that when nucleons fuse they lose mass (I notice too late), is this the Gamma Ray source in 2nd step? from the lost mass of the protons? if it is, would you kindly explain how much MeV the mass loss in step 2. I'm very appreciate your concern, thank you.

That is correct, the mass is converted to energy (gamma ray photon) in the second step.

Isaiaswolf66 Yes, I misspoke. It is indeed a gamma particle.

Not sure what you mean by "proton - proton barrier height is 400 keV and how that is directly related to the temperature needed for nucleur fusion". Calculate the velocity needed for a proton in order for it to approach another proton close enough for the nuclear interaction to occur.. (For the nuclear strong force to be larger than the proton-proton repulsion. )

when someone says: 4 hydrogen are converted into 1 helium, they are talking about the net process. Looking at the details of the proton-proton chain process, there are indeed multiple steps during which protons are fused and converted into a nucleus containing 2 protons and 2 neutrons which requires 2 protons to be converted to 2 neutrons through the ejection of a anti-electron (called positron).

Thank you for the anwser. It makes more sense now.

+juan cuello espinosa When nucleons fuse, they lose mass. The mass of an alpha particle 3727.38 MeV/c^2 is less than the mass of 2 protons (2 x 938.28 MeV/c^2 and 2 neutrons (2 x 939.57 MeV/c^2:

A proton is made from 2 up quarks (each have a +2/3 charge) and 1 down quark (which has a -1/3) charge. When a proton converts to a neutron, one of the up quarks is changed to a down quark. A neutron has 2 down quarks (-1/3 charge each) and 1 up quark (+ 2/3) charge which makes the neutron neutral. The mass of the 3 quarks by themselves are just a tiny fraction of the total mass of the neutron or proton, thus the mass is formed through an energy conversion when the 3 quarks join together to form a baryon. It appears that the neutron is given a slight amount of additional mass over a proton.

@@MichelvanBiezen Thanks my man. I need more readings... XD I watched another video that says that "the mass of the 4 protons is greater than the mass of a helium (alpha particle) in a proton-proton CR. I would love to hear your explanation about that matter. More power!

That is a good question that we don't have a good answer for.

The mass of the individual 3 quarks that make up a proton or that make up a neutron, when measured individually is much less than the mass of the proton or neutron. The mass of an up quark is approximately 2 MeV ( 2 mega electron volts energy to mass equivalence) and the down quark is about 4.8 Mev But the mass of a proton or a neutron is about 938 MeV.

@@MichelvanBiezen Alright, thanks for the reply! :)

about 24.7 MeV

According to my book and Wikipedia energy released is 26.7 why ?