The mod simply renders the solar system planets in Minecraft's skybox during the night. In a way, the MC skybox is a planetarium if you think about it. The planet textures are made by @Crackers0106 (PR woodiertexas#1) and @lxly9 (PR woodiertexas#2).
The project source is licensed under the MIT license whereas the project assets are licensed under the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License.
I personally welcome third party ports to previous minecraft versions, but I respectfully ask that you do not port to (neo)Forge or Fabric.