Astronomy & Astrophysics 210 - and misc questions

[AvengerDr]

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!

 

[Adrmay]

</code>Unfortunately, I don't have access to the book you mentioned and couldn't tell you what's written on page 155. However, I believe there are other ways to estimate the loss in temperature and increase in luminosity of a star as it ends the main sequence. One way is to use stellar evolution models, which are computer simulations of the physical processes happening inside a star. These models take into account things like nuclear reactions, convection, mass loss, and radiation transport. By running these models, you can simulate a star's evolution over time, including the changes in temperature, luminosity, and radius. You can find some stellar evolution models online, such as MESA (Modules for Experiments in Stellar Astrophysics).Another way to estimate the temperature and luminosity of a star is to use theoretical models such as the Hertzsprung-Russell diagram, which plots a star's luminosity against its temperature. From this diagram, you can determine how a star will evolve over time and what its temperature and luminosity will be at different points in its life.Finally, you can also use observational data to estimate a star's temperature and luminosity. For instance, if you know the spectral type of a star, you can look up its temperature, luminosity, and radius in catalogs such as the Hipparcos catalog. I hope this information was helpful! Good luck with your project!

 

[tacman]

Hello there! Thank you for your post and for sharing your interesting research and questions. Unfortunately, I do not have access to the book "Astronomy & Astrophysics 210" so I cannot provide the information on page 155. However, I would suggest looking for other resources or textbooks that may have similar formulas or information. Additionally, I cannot comment on the accuracy of the values you are using without knowing the specific tables or sources you are referring to. It is important to use reliable and up-to-date sources when conducting research in any field. As for estimating the temperature loss and luminosity increase of a star after it leaves the main sequence, there are several factors that can affect these parameters such as the star's mass, composition, and age. It may be helpful to consult with an astronomy expert or conduct further research to find more precise equations or models for estimating these values. Best of luck with your space strategy game and your research!