is there anything better than this
Well that renderer is quite beautifull but I don't think it has any kind of realism at all. Rendering nebulaes is surelly a difficoult task.
Or any alternatives for making/rendering planets than Terragen or Grand Designer?
Outerra is quite fantastic in rendering planets from close to the surface views. Check this
As SpaceEngineer said:
Outerra is not a procedural generated planet. It uses NASA's 90m SRTM data (landscape data with 90 meters resolution), and some noise functions to generate details. In SE I will use such a technique too for Earth, Mars and other real planets. I'm surprised why Cameni doesn't use NASA's color textures (Blue Marble Next Generation) to texture upper LODs of the planet. From high altitude and space it looks strange.
So SE is going to be waaay better than Outerra in the end (if there is an end).
And for the most amazing renders of Mars you have to check this channel. Here you have a demo for a VR trip over the high resolution data of MRO. It's amazing