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Homework Help: Gravity help please

  1. May 9, 2006 #1
    can u help me to explain the role of gravity in the equilibrium of stars in their production of enegry , and an explaination of the role of gravity in the formation of planets.
  2. jcsd
  3. May 9, 2006 #2
    quick and dirty answer

    Basically stars are converting hydrogen into heavier elements (a process known as fusion), which released heat in the process. This heat attempts to make the star expand, which is held in check by the immense force of gravity.

    A couple things to note:
    1) It is gravity that is responsible for starting the fusion process. The stars accrete matter until they have a critical mass, at which point the gravitational force acting on the atoms causes them to undergo fusion.

    2) As the star "burns" (it is not on fire, fire requires oxygen) it loses mass. This reduction in mass means that, over time, the gravitational force will not be enough to hold the star together. At that point we get a fireworks display known as a nova, or if the star is large enough, a supernova.
  4. May 9, 2006 #3


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    Staff Emeritus
    Science Advisor

    Please do not double post - this question was posed yesterday. One should search for missing posts before reposting.

    As for fusion - it's the temperature (or kinetic energy) of the nuclei that control the fusion reaction rate. Gravity holds it together.
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