pablo-mayrgundter
commented
3 years ago My current sim yields galactic arms by virtue of an initial-condition hack that sets up dense arms and then sets them swirling but this leads to increasingly thing arms over time. It's also flat. Unfortunately both dynamics are incorrect :(
Stable spiral arms
"Originally, astronomers had the idea that the arms of a spiral galaxy were material. However, if this were the case, then the arms would become more and more tightly wound, since the matter nearer to the center of the galaxy rotates faster than the matter at the edge of the galaxy.[6] The arms would become indistinguishable from the rest of the galaxy after only a few orbits. This is called the winding problem." - https://en.wikipedia.org/wiki/Density_wave_theory#Galactic_spiral_arms
Which it seems has a rich research history to explore: "Six Decades of Spiral Density Wave Theory".` Shu, Frank H. (2016-09-19 linked in Wiki)
This video also explains it:
Galaxies Don't Spin The Way You Think | 4K
Here's a beautiful sim with 20k stars in webgl, but it does degenerate from the winding problem. If you let it run for a while the number of periods increases continually, squeezing the initial spirals until they're whispy thin:
Large-scale warp
It has been observed that the Milkyway has a warp to it from extra-galactic gravitational stretching:
Milky Way Galaxy Is Warped And We Now Have a Map Of It!
The warp might be well achieved by simulation, e.g.:
- Two Galaxies by Evgenii Neumerzhitckii
- Logarithmic potential (optional two galaxies) by Adrian Price-Whelan
More on the logarithmic distribution potential: https://www.astro.rug.nl/~vdkruit/jea3/homepage/dynamics.pdf
@85332266b62586cb7f532bff6efe0aaa132398fa has a basic pinwheel galaxy.
Next up I think is to use instanced points as a stamp to fill in around each point in the simulation:
https://www.google.com/search?q=threejs+instanced+point+cloud&oq=threejs+instanced+point+cloud&aqs=chrome..69i57.5730j0j1&sourceid=chrome&ie=UTF-8 https://jsfiddle.net/h9fnx3sy/ https://stackoverflow.com/questions/42791295/instancing-pointcloudparticlecloud-in-three-js https://github.com/mrdoob/three.js/blob/master/examples/webgl_points_dynamic.html
https://user-images.githubusercontent.com/2480879/104142205-8364a180-5388-11eb-95dc-b5c5ae51afd3.mov