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Mass fraction?

  1. Nov 8, 2007 #1

    malawi_glenn

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    Hi!

    I am reading text in metal abundances, for example one of my books states that the metallicity of the milky way is:

    z = 0.02

    etc.

    Is that mass or number fraction? I have searched in all my books and google a bit but can't seem to find an answer :S

    Help
     
  2. jcsd
  3. Nov 8, 2007 #2

    jim mcnamara

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    Metallicity is defined as the proportion of mass in an object that is not hydrogen or helium - could be carbon, iron, whatever else. Metals in this case are not the metallic elements as we think of the term. Carbon is a metal in this case, for example.

    It is the [tex] metal mass / total mass[/tex]

    It's a fraction.
     
  4. Nov 8, 2007 #3

    malawi_glenn

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    Great thanx!

    I know all the other stuff you wrote, was just unsure if z is number or mass ratio.
     
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