I started working on a stellar system generator. those I've found on the web are not really good.
Most seems to use random numbers or have an obscure method. For example, one had as much chances of generating an class M star as an F star, which is extremely inaccurate.
I think I managed to do something not too bad by using as much real world data as possible.

GOAL: generate stars (single and multi star systems) and their planets with some basic information

So far, I have the stellar class distribution.
I have the probability of how many stars there is for each system.
I can generate each star independently or in groups.
Then, figuring out how many planets there are in each system. We don't know how many planets there are so I've made my own distribution with an average of 6 planets per systems.

In the last part, I assign different planets to different star categories.
Flare stars, about half of the M stars (or 38% of the total) have different planets because the flares tend to strip the atmosphere of the planets and cause massive radiations. Lastly, like others M star, these stars are cold/dim, in order to be warm enough, planets need to be quite close and will be tidal locked in many cases.
White dwarfs are another poor candidate for good planets. These stars are dying and have gone through massive changes (novae). Whatever lived there before is dead but life can begin anew after the star has "stabilized". The problem is that these star emit massive radiations and planets need to be so close to them (in order to be warm enough) that they are almost tidal locked, which is a big problem for life.
The most massive stars (O,B A) die too young to have planet able to support life. They are also less likely to have planets I think, planets don't have enough time to form before the star dies.
The remaining stars with the most potential are F,G,K and M. Although I might further split M stars for those that are the dimmest : planets located in the habitable zone are tidal locked.

As I said, each kind of star have different planets. I made some classification and i would like some thoughts about it.

Those I have at the moment:


  • Barren: no atmosphere. example Mercury (well Mercury does have some kind of atmosphere but it's marginal)


  • Ice: covered by a thick layer of ice and snow, might have a thin atmosphere. They are unlikely to have any by scifi depict them with breathable atmosphere. Hoth.


  • Desert: dry, tends to be hot. Mars, Tatooine.


Earth like planets: maybe the categories are redundant. They are all habitable but have different temperatures/moisture level.

  • Tundra: milder than the ice planet, can support an atmosphere and complex lifeforms without requiring terraforming. Earth during the glacial age


  • Arid: More humid than the desert planet and can easily support an atmosphere with life. This is what a terraformed Mars could look like.


  • Temperate: This is Earth. Also include the ocean planet type. The only difference is that they have few landmasses.


  • Jungle: warm and humid. it is possible to have the whole planet as a rainforest with the right atmospheric composition. mezozoic Earth, Dagobah



  • Toxic: the planet used to be an Earthlike planet but gradually became closer to hell. Rising temperature made the oceans boil and to the point where water vapour was expelled from the atmosphere by the rising pressure. These planets have dense and hot atmosphere. Venus.


  • Superearth. Planets similar to Earth except they are a lot bigger, have higher gravity, tend to have a denser atmosphere. In my definition, these planets are not gas dwarf, and are limited to planets that could support life.


  • Gas giant: I included all the gas planet together. My main concern is toward habitability so i don't have an incentive to differentiate these kind of planets. These planets are usually heavier than superearths and have a thick gaseous envelope.


  • Brown dwarf: technically, these are failed stars but there could be so many that I prefer to classify them as large planets. These are usually a few times the mass of gas giants. Unlike real stars, they are not massive enough to fuse atoms. They still produce heat but they are extremely cold even compared to the average M stars. They can have their own systems, called rogue stars, but we don't have a lot of info on them because they are too dim to see.


About the planet distribution: since we know very little on exoplanets, this is going to be a lot of guesses. Some things are more obvious than other: I've set 85% of all planets to be barren with flare stars. I guess a planet can be dry or covered in ice but without an atmosphere, it's not much different from a barren planet. that's why I'm wondering if some of the categories are redundant or just not well defined.