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Dwarfs and energy

  1. Sep 28, 2003 #1
    According to my Geology textbook (it is about astronomy, i wonder why we have this in the Geology textbook) :
    (sorry if translation is not really good)
    The text may seem a little bit confusing, but let me give you the summary.
    The book says that a star may become a dwarf when the nuclear reactions in it stops, and later the book says that dwarf have high temprature.
    My question is: Where does the temprature of the Dwarf comes if the nuclear reactions are over ?

    Thanks in advance.
  2. jcsd
  3. Sep 28, 2003 #2


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    Greetings !

    Once most of the hydrogen burns out in nuclear fusion
    the dominant reactions become nuclear fission. This
    heats up the star and makes it expand to giant(relativly :wink:)dimensions. Eventualy the core cools somewhat and collapses.
    The violence of the explosion, if any, and what the star
    eventually ends up as - BH, neutron star, white or red
    dwarf depends on its enitial mass.

    Live long and prosper.
  4. Sep 28, 2003 #3


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    Re: Re: Dwarfs and energy

    Oh sorry... anout the dwarfs, well, nothing really
    powers them - just some little random remaining nuclear
    reactions and its enitial temprature as it cools.
    It can not collapse into denser objects because
    it's not sufficiently massive.
  5. Sep 28, 2003 #4


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    AIUI, the energy in a dwarf star is from the collapse itself, plus left-over energy from previous fussion. Though fussion is no longer taking place in the core, the dwarf is a star that used to be a giant, and has fallen in on itself. The particles of heated gasses falling in toward a central point collide with one another, and this collision generates heat. This heat is trapped by the great density of the dwarf star, and takes a very long time (even in cosmological terms) to radiate away.
  6. Sep 28, 2003 #5


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    Just to add to what LURCH said.

    The dwarf, once the collapse has settled down, slowly cools by radiation. This takes a long time because the dwarf is so small.

    If the dwarf has a close binary companion, or close planets, it may experience some heating at a future time, as material from its companion falls onto its surface or a planet is gobbled up.

    Also, through orbital interactions or magnetic braking, some of the dwarf's rotational or magnetic energy may be converted into heat.
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