Re: [nbos] Mass Luminosity Relationship
"Dalton Calford"
Fri Feb 22nd, 2008
Thanks Justin, I will see what I can do about finding out the alpha

On Fri, 2008-02-22 at 12:37 +1100, Justin Akkerman wrote:
> G'Day, I go this from a text called "Introductory to Astronomy and
> Astrophysics" 2nd Ed by Zelik and Smith. Page 216 has the following
> Luminosity/Luminosity(sol)=(Mass/Mass(sol)) raised to Alpha.
> Alpha is not a universal constant. It is about 2 for dim red stars of
> low mass. It is about 3 for high mass luminous stars. It is equal to
> about 4 for solar type stars.
> Assuming you know the Luminosity, the star type and want to know the
> the mass you would write the equation in excel as follows:
> MassStar=MassSun(LuminosityStar/LuminositySun)^(1/Alpha)
> The M-L Law does not apply to Red Giants - they have large extended
> atmosphere which add considerably to their radius nor does it apply to
> White Dwarfs - they contain degenerate matter rather than normal
> plasmas.
> There is a relationship called the Russel-Vogt Theorem which has only
> one solution for the parameters Mass, Radius and Luminosity is one of
> them and the chemical compositions of the star are known. This was
> only described in words, not spelled out in equations. Maybe this
> theorem is beyond and introductory text.
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