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Name: Yonggang
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Question:
Why there is no proton stars or electron stars supported by degeneracy pressure? I think in this range they may be attracted by strong interactions which can overcome the electromagnetic interactions like the forming of nucleus. I know the heaviest nucleus has a mass less then 118 but it may be due to the mixing of proton and neutron prevents its getting heavier? I do not know whether the density of neutron star is the same with nucleus or much less than nucleus.



Replies:
Yonggang,

One great "problem" with forming a star from neutrons is that protons can easily join together to make larger atoms. Two protons fused together into hydrogen-2, with the release of an electron and an anti-neutrino, has less energy than two separate protons. The strong force has no preference for protons or neutrons. Dropping an electron does not disrupt the strong force. It does however "relieve" the electroweak force. (At high energy and density, electromagnetic and weak forces join into one effect). This hydrogen-2 nucleus then fuses with another proton to produce hydrogen-3, releasing an electron and an anti-neutrino. Two hydrogen-3 nuclei can then fuse into helium-4 plus two free protons. Overall, this process leads to less energy and greater density. A proton star is essentially what a star starts out as, not what it ends up as.

As for electrons, they cannot feel the strong force. Just as the electromagnetic force exerts its effects on electric charge, the strong force exerts its effects on what could be called strong charge. This is very different from electric charge. It is often called "color". Color does not feel electric force. Electric charge does not feel the strong force. Electrons have no color to them. Protons and neutrons are composed of particles with color called quarks, and so they do feel the strong force.

Dr. Ken Mellendorf
Physics Instructor
Illinois Central College



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