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Allright I am a 17 year old student, that only just figured out that the universe is amazing!

Thanks to Dr. Neil Degrasse Tyson I raised a lot of interest in the universe. Due to his latest show "cosmos".

So I started thinking about a lot of things including. How does the sun burn without oxygen?

It might not be burning but a big part of the society speaks of it as burning.

So how does it work?

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I share your view of the universe and the more I learn the more it increases my amazement! – Itumac Apr 29 '14 at 20:44
This question on the Physics site is similar. (I think it was originally posted on the old Astronomy site, which was shut down and merged into Physics before this new Astronomy site was created). – Keith Thompson Apr 29 '14 at 21:48
up vote 7 down vote accepted

As you are suspecting, the sun burns in a different sense, not by chemical reaction with oxygen.

Atoms consist of a tiny, heavy nucleus, surrounded by an almost empty space, populated by electrons. Burning by chemical reaction with oxygen doesn't change the nucleus of atoms, but takes place in the hull of atoms: Atoms may assemble to form molecules; electrons change their orbitals (the way they surround the nucleus), and release some energy as heat.

Atomic nuclei are (positively) electrically charged, and repell each other. But if small nuclei, like those of hydrogen atoms, come close together, they can fuse and form a larger nucleus. This nuclear fusion of hydrogen to helium (in this case) releases much energy, more even than fission of uranium in a nuclear power plant. The notion "burning" is used sometimes for reactions of atomic nuclei, too, if they release energy as heat.

To overcome the electrostatic repulsion of hydrogen nuclei, high pressure and temperature are needed. These conditions occur in the core of the Sun.

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At the core of the sun the gravity is so strong that atoms of Hydrogen do not exist, instead we have a mix of protons and electrons initially.What starts the sun shining is the fusion of these protons,in various sequenced patterns. Firstly we have the proton-proton chain, yes, you guessed it, they smash into each other and release energy,and through another process one of those protons turns into a neutron that combines with another proton, making dueterium (a Helium nucleus) and this dueterium can also get hit by another free proton,or even another dueterium nucleus, with the release of more energy and more nuetrons etc in a chain of reactions that continues on like this to produce a lot of energy and eventually all of the hydrogen and helium will be "burned" up and turned into larger heavier elements,the sun can fuse these too...right up to when iron nucleus is formed,at that point the stability of the iron prevents any more fusion reactions.Getting back to the core,the light energy that is formed at the core has to "skip" accross an absurd number of particles to eventually make it to the surface and radiate out of the coronosphere,in fact it takes millions of years for that energy to escape from the core! If you wany a detailed explanantion of the proton-proton chain (and other chains) google it.

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