# Mass radius relationship for SIRIUS B

by cooper607
Tags: mass, radius, relationship, sirius
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 P: 49 hi guys, I have been doing a research on white dwarf stars and chanrashekhar limit. I need to plot a graph for the mass-radius relationship of the dwarfs. from the equalization of the hydrostatic equilibrium pressure and the electron degeneracy pressure I found out the radius -mass relationship for non relativistic fermi gas. my final result is R=3.58*10^16 M^(-1/3) but when I take relativistic fermi gas, pressure comes in order of 4/3 and the radius cancels out leaving the equation to be M(limit)=1.44 M(sun) Now for this maximum limit how can I plot a graph for radius vs mass. which values should i input for different masses? please help me
 Sci Advisor P: 2,684 What do you mean plot a graph of radius vs mass for a limit? The limit is one value. It's a dot. What is the radius at this mass? If your final result is correct, you need only input this M(limit) into M.
 P: 49 But the relativistic fermi gas plot is different than the non relativistic, i want to know how do they get this graph? Attached Thumbnails
 Sci Advisor PF Gold P: 9,372 Mass radius relationship for SIRIUS B The formula can be found here - http://burro.astr.cwru.edu/Academics...WDmassrad.html. It is interesting to note that the radius actually shrinks as mass increases.
 P: 49 dear Chronos, I actually visited that page earlier, for relativistic fermi gas they derived the relation to be 1=M^(-1/3) , so radius actually cancels out from both sides. so how do they plot that graph where radius is zero when mass goes to 1.44? i didnt get any expression for the graph..can you tell me if there is any radius -mass relation for the relativistic curve ?

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