Felipe Tavares' Avatar

Letter to an Astrophysicist

September 11, '19

Hi dear Astrophysicist,

I am Felipe.

In short, I am a not-even-undergrad who is obviously a bit(?) too dream-y.

So, here we go: for the purpose of a game I am interested in the simulation of galaxies, more specifically in the evolution of the distribution of mass in space over time. I am also interested in the flux of stars and the reflectance of dust clouds and gas (possibly any other photon-emitting or reflecting phenomena).

I find those interesting because they are directly related to the data I need to render pretty pictures of galaxies, which is a big part of games, and even more of space games.

I could, of course, just replicate existing data which we have in tons about those properties (well, maybe not so much about dust clouds?), but it just so happens that I like creating games based on procedural generation, which inside the gamedev community is a term used mainly to define the creation of content based on systems that replicate physical ones or are in some other way “interesting”.

My initial thesis, which I do not know if holds, is that it is possible to simulate the visually interesting parts of galaxies (for example obtaining stuff that looks similar to Hubble’s galaxy classification) without using a super computer and lots of time, if you drop all ambition to be physically correct and instead focus in the reasons why different systems balance out and in creating the simplest simulation that balances in a similar way.

I know that for gas simulation it is not really possible to simplify that much, but for the initial part of this project I was hoping to use simple statistical models for star formation and death in such a way I hadn’t to actually simulate gas in detail.

Now, the first thing I did was creating a simple n-body simulator with a very small number of particles (n=1000) and just seeing what happens. No results there of course, there is much more to galaxy simulation than gravity (I used MOND to avoid having to simulate dark matter and dark energy, hopefully).

The thing is, I don’t know exactly what is the “more”. After some studying I have some candidates, but I am not sure how big of a role each of those play. I was hoping there was some function that dominates the “that’s why galaxies look like that”. I am sure gravity is one big component but besides that there is obviously something there.

First thing I thought was of course, overall mass distribution. With a uniform distribution, you don’t get anything interesting at all.

Second thing was star formation, which seems to be a good guess since AGN appears to be an important component of realistic simulations and also tied strongly to star formation.

Third thing was gas simulation (which I seriously hope isn’t the case given the computational power needed to simulate even the more simplistic gas models).

Am I on the right path here? What should I be studying to get this big picture of galaxy formation without getting too tied up in specific details of our specific universe? (is it possible?)

I am trying to study using “Galaxies in the Universe: An Introduction” by Linda S. Sparke and John S. Gallangher but it seems that there are just parts where it goes way faster than I can go by showing graphs which I can’t seem to get a grasp of and the going at rocket speed from there (the first part this happened was after the initial discussing on blackbody approximations and flux), and there is also the fact that my interests seriously diverge from the average undergrad studying the book, which results in me, looking at the ceiling and wondering what have I got myself into (and should I skip this? or shouldn’t I?).

Can you help me with any of this (hopefully not much) nonsense?

If you feel you can, please drop me a line!

Sincerely, Felipe Tavares.