Detail this asset from Unity Store: Original Link
This is a paid asset, but now you can download 4K Space Skyboxes Free.
4K Space Skyboxes
This package contains 40 space-themed skyboxes, each featuring six 4k (4096×4096) png textures – perfect for projects requiring high definition visuals.
240 textures in total, each of which are seamless (as per the materials they are assigned to) and unique – no repetitions!
These skyboxes are themed as follows:
– blue nebulae
– firey nebulae
– mixed nebulae
– monochrome (for B&W projects, and also to allow the use of a uniform colour tint)
– nebulae only (in case your project requires a third-party starfield)
– starfields without nebulae
All the nebulae have been pre-rendered with a volumetric effect, to give an impression of realistic, internal illumination.
Plus – no lens flares!