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Astronomy & Astrophysics 210 - and misc questions

  1. Sep 6, 2007 #1
    Hello there,
    I was searching the net to find some empirical formulas on how to estimate the loss in temperature (and increase in luminosity of a star as it ends the main sequence. I've found that some of these formulas could be located in a book called "Astronomy & Astrophysics 210" by Maeder A., Meynet G., 1989. Unfortunately google books doesn't seem to have that book online. I was wondering if anyone here had this book and could tell me what is written on page 155.

    I realize that probably that book isn't the "holy grail" of such estimates, but since I'm developing a space strategy game I'd like to know how to empirically "evolve" stars that left the main sequence, IF it is possible in some way. I'm basing my star-creation algorithm by determining a solar mass at random (based on the known distribution of stars: there are more red-dwarf sized stars than others) then interpolating that value onto a table of absolute bolometric magnitudes and effective temperature. I then use these values to determine the bolometric luminosity and the solar radius. I'm using the values found here.

    Could anyone tell me if those values are accurate? Because I've found several tables on the net but no one seems to agree with each other. I do know that those values can change even drastically, but I'd like to know from the more astronomy-savvy if those values I'm using are sufficiently accurate or not. Calculating the lifespan with the formula Mass/Luminosity I can discover how many Gy the star will live, but after that, is there a way to estimate the temperature loss and luminosity (and radius) increase?

    I decided to interpolate the mass on those tables to find the bolometric magnitude and temperature, because using the mass-luminosity relationship (L~M^3.5), resulting values were not very accurate (at least if compared on those tables), and I needed at least another parameter to calculate the radius (R=L^1/2(T/T*)^2) and the luminosity (L* = 10 ^ (0.4 x (4.75 - mb*))). Is there some other way to calculate these stellar parameters in a more precise way? Because as far as I understand (unfortunately I have a degree in computer science) these equal symbol in these formulas tell me that these quantities are perfectly equal and are not approximations, therefore values computed in such way should be more precise.

    I'll use those parameters to then simulate an accretion-like model of planetary formation which I based on previous implementations of the original Accrete model by Stephen Dole. I already implemented it and it seems to work, computing almost every parameter imaginable :) The only thing it is missing is a simulation of the evolution of the atmosphere (which seems a daunting task) and if the hydrographic coverage estimates takes into account the possible presence of oceans not based on water (like ammonia or methane).

    Thanks in advance!
  2. jcsd
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