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(electron)Degenerate matter

  1. Sep 21, 2006 #1
    I am trying to find good info on (electron) degenerate matter. Im going to write a report and do a 25 minute presentation on white dwarf star matter and metallic hydrogen in gas giants but I have a hard time finding good info. What I need to know most is how the atoms are effected by the insane preasure.

    Anyone got any hints on where I can start looking? What review journals, textbooks ect.

    Any help would be hughly appriciated:approve:
  2. jcsd
  3. Sep 21, 2006 #2
    Well as for sources i am unsure, my uni text book was quite good but im not sure it will be avaliable where you are.

    I assume you are talking about core collapse supernovae which involve degenerate matter. In this case i can offer an explination (well ill try)

    without going into to much detail, just before a SN occurs you have material being deposited on the core from the fusion reactions going on that cannot undergo exothermic fusion. That is to say when you fuse stuff normally and deposit it on the core the temperature isnt high enough to fuse that product initially but gets there over time and you get shell burning etc. BUT when you hit Iron, you get a problem. Iron is the most stable element in terms of nuclear processes. That is fusion of iron atoms actually requires energy rather than releasing it. This means that you get the mass of the core building up with none of it being consumed. Once you reach a critial mass of sorts, roughly 1.5 solar masses i think, you find that the intest pressure and temperature, ie the weight of the star above the core, is so intense that it causes protons and electrons to fuse together to form neutrons. This is basically pressure overcoming the quantum mechanical properties of the material, a pressure so high it can overcome electron-electron repulsion (and the same for positive charges obviously)

    the result of this is interesting. as you know atoms are mainly empty space with massive distances between the nucleus and the electron shells. However, if you have something composed of degenerate matter, ie neutrons, you have no charge repulsion and so the max density is massively higher. This means when the core becomes neutron matter, it collapses in and shrinks to about 10% of its size in about 3 seconds (not sure exact numbers) . This leaves a huge gap between the material above the core and the core. Effectively the star falls in at a good percentage of the speed of light, hitting the core and bouncing off in the, aptly named, core bounce. This is your supernova explosion.

    Sorry if this didnt answer your question but i wasnt 100% sure what you were asking so i gave a general statement
  4. Sep 21, 2006 #3
    thanks. Hit me with the textbook and Il se if I can find it in a library around here :)

    I wasnt realy looking for neutron degenerate matter though. Matter in white dwarf stars and inside gas giants are electron degenerate. while neutron stars are neutron degenerate. Same principle I guess but neutron degeneracy is one step close to total collaps.

    In electron degenerate matter the degeneracy pressure arising from electrons trying to squeese into eachothers orbitals are enough to fight of the gravity.
  5. Sep 21, 2006 #4
    Im mostly interested in how the atoms and its orbitals are effected in situations like that. How the wavefunctions mix. Not so much the general macroscopic properties of electron degenerate matter.
  6. Sep 21, 2006 #5
    Ah ok, then this book probably wont help. I dont think it goes into that much, but just for kicks its called Universe 7th edition by Freedman and Kaufmann III. its really good.

    Making an educated guess id actually think that there would be very little actual 'motion' due to the pressure untill the collapse. THat is up untill the point where the QM properties are overcome id think the shells would be in more or less the same place
  7. Sep 23, 2006 #6
    The Runaway Universe might be good too. It talks of the white dwarf where the gravity pulls the matter so close that the only thing keeping it from collapsing is the uncertainty principle. As a result information cannot be transfered across the star too quickly which causes a SN1A when a partner red giant feeds the dwarf enough that it gives it enough gravity to overcome uncertainty.
  8. Oct 8, 2006 #7
    I realise it might be to late for your report, but here is some info about electron degeneracy quoted from "The five Ages of the Universe" by Adams and Laughlin, page 48:
    "A billion years or so after hydrogen is first depleted in the center of the sun, the exhausted central core becomes so dense that most of the pressure is provided by degenerate electrons. The term degenerate is used here in the quantum mechanical sense. Electron degeneracy is primarily a consequence of Heisenberg`s uncertainty principle. As electrons are forced to occupy smaler volumes, their velocities mount, and the pressure they produce increases. A stellar object supported by this pressure is called a white dwarf..."
  9. Oct 9, 2006 #8


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