Solar System

Changed the skybox to a darker one from here:
https://assetstore.unity.com/packages/2d/textures-materials/milky-way-skybox-94001

Made a corona for the Sun using the bloom post-processing effect:
https://gamedev.stackexchange.com/questions/175871/how-to-create-a-glowing-corona-halo-around-a-sun-and-make-it-emit-light 

Made the water on Earth smooth (thus more reflective), while the land is not. Using the alpha channel of the metallic map texture (which I created in PaintShop Pro from the albedo texture).

Added all the planets. Tweaked the orbital speeds, distances, and surface reflectivity of each planet.

Added trail renders to each planet for the Minimap Camera (using a separate layer) to show the orbital paths.

Added another Comet Spawner and changed them so that the comets fly in crossing the orbital plane (as they do).  Used this sound effect for the planets:
https://freesound.org/people/Wesselorg/sounds/408442/
Modified it in Audacity to loop better.

CREDITS
A game by Raimond Tunnel
Whoosh SFX by Freesound user Wesselorg
Skybox by Adam Bielecki