[Mesa-users] Question about mass fraction

[amber lauer]

A useful column is the dm, which lists the amount of mass for each zone. If
you weigh the mass fractions in each zone by this value and sum them you
can get mass information for larger regions of the star. This is
particularly useful if one wants to compare MESA results with observation,
which are presumably limited to the photosphere. The equivalent region in
the star would be down to the depth where Tau (the optical depth) is ~1
(although other sources disagre on the exact value of this depth for the
photosphere).

=================================
Dr. Amber Lauer
Postdoctoral Researcher
Triangle Universities Nuclear Lab
Duke University
amber.lauer at tunl.duke.edu <amber.lauer at duke.edu>


On Fri, May 17, 2019 at 9:28 AM Francis Timmes via Mesa-users <
mesa-users at lists.mesastar.org> wrote:

> since a mass fraction is a mass divided by a mass,
> a mass fraction is dimensionless (no units, a pure number).
>
> fxt
>
>
>
>
>
> > On May 17, 2019, at 4:45 AM, d10631026陳瑜安 <d10631026 at gapps.fg.tp.edu.tw>
> wrote:
> >
> > How can I mark the unit of mass fraction?
> >
> > d10631026陳瑜安 <d10631026 at gapps.fg.tp.edu.tw> 於 2019年5月17日 週五 下午3:08寫道：
> > Thanks!
> >
> > On Fri, May 17, 2019, 11:57 Francis Timmes <fxt44 at mac.com wrote:
> > in simple terms, the mass fraction of a substance within a mixture is
> > the ratio of the mass of that substance to the total mass of the mixture
> >
> > X_i = mass_i / mass_tot
> >
> > since the individual masses sum to the total mass, the mass fractions
> sum to unity
> >
> > sum X_i = mass_tot / mass_tot = 1
> >
> > your picture seems ok.
> >
> > fxt
> >
> >
> >
> >
> > > On May 15, 2019, at 7:32 PM, d10631026陳瑜安 <
> d10631026 at gapps.fg.tp.edu.tw> wrote:
> > >
> > > Dear MESA Users,
> > >
> > > I'm not sure whether the meaning of mass fraction is like what I draw
> in the picture.
> > > I would like to ask about the meaning of mass fraction.
> > >
> > > Thank you,
> > > Ann
> > > <QUESTION.png>_______________________________________________
> > > mesa-users at lists.mesastar.org
> > > https://lists.mesastar.org/mailman/listinfo/mesa-users
> > >
> >
>
> _______________________________________________
> mesa-users at lists.mesastar.org
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>
>
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