Nice work. You briefly mentioned curl noise... About 10 years ago I wrote gaseous-giganticus[1] which uses curl noise to create gas-giant planet textures. They don't move, like yours, but don't look too bad (and looking at Jupiter, you can't really see that move over small time scales anyway.) Some animation is possible[2] with gaseous-giganticus, but not in real time, as it's all done on the CPU, and it doesn't really sustain over time, as it starts off looking very fuzzy, resolves into something pretty nice, then gets weird. Here is some more output from early days: https://imgur.com/a/9LipP
Really cool - thanks for sharing! I thought about using cubemap to have the whole planet simulated but, since I only use the effect as a part of a skybox, it would be wasteful. You also use particles instead of textures. Are you familiar with the work of Larry Yaeger and Craig Upson? They created Jupiter for "2010", and used similiar, particle based approach.
Here are some slides about the development of gaseous-giganticus (best viewed with a real computer, not on a phone, as it uses arrow keys to navigate the slides): http://smcameron.github.io/space-nerds-in-space/gaseous-giga...
[1] https://github.com/smcameron/gaseous-giganticus [2] https://imgur.com/mqCwMeI