# B Generating Plausible Star Systems

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1. Feb 28, 2017

### Dyrakean

I'm trying to write some code to generate plausible star systems, but so far, I only have a main sequence star generator, and even with that I don't know how good the mass-radius relationships are. So, I'm coming here to ask for some formulas or pointers as to where I can go to find the math to figure out...

1. How big stars should be (Radius based on mass)
2. Mass range of stars
3. Placement of planets (How to calculate volume around a star where planets can form, and how close planets can be depending on their masses)
4. Mass-Radius relationship in planets of all forms (terrestrial, gas giant, etc.)
5. Whether a planet can have moons, and if so, how many and where to place them
6. What type/size/number of planets is likely to form around a given star (It's probably more complex than just based on mass, but for the purpose of this we can ignore everything but mass (You know, if that's possible) )
7. Placement of stars in a galaxy (How close can the orbits get before planets get disturbed or they risk collision)
And whatever else may be relevant. I've done a lot of looking to try and find answers for this, but I'd like to ask here to confirm what I've found, and many of these are still unanswered.

Last edited by a moderator: Feb 28, 2017
2. Mar 1, 2017

### amarante

Hey, I don't know how accurate you want it to be.. anyway here are some info that I can quickly mention.

1. The mass-radius relation of stars can be checked in the lecture here: link and on this paper: link. The lecture is based on the book "stellar structure and evolution" - Kippenhahn & Weigert, so you can trust. The link for the paper redirects you to ADS abstract service. If you want more information about it, you can check the citations of the paper and also the references they provide.
2. I would say that the minimum stellar mass would be ≈0.08 $M_{\odot}$, less than this would be the brown dwarf limit. The upper limit it depends on what do you want... you can find some very massive stars, but they are really rare. Here is a list of the most massive stars: link
3-6. This is mostly based on planet formation studies. The radius/mass relation is based mostly on the model due to the lack of real data on that, but some of the planets have the mass and radius estimated... You can check this exoplanet encyclopedia. And this paper for an estimation of earth like planets around stars based on Kepler data: link. For 6 you can use the data from the exoplanet encyclopedia and check the how the is the distribution of mass of the planets according to the stellar mass... but this is going to be biased due to the fact that it is easier to detect earth-like planets in low mass stars.. but anyway it is a good way at least to check it with some model of planetary formation.
7. Do you mean how are stars distributed on the Galaxy halo, disk and bulge? This paper is good to give you an idea how is the distribution of stars based on star counts.

Sorry for not being able to give any more detailed explanations.. but at least you can check some info in the links I have send.

3. Mar 1, 2017

### Dyrakean

Thanks for the response! I haven't seen these yet, so I'll take a look and see what I can work out from it.