I remember a couple of things, eg you could compare planet sizes to one another. For instance comparing the sun with the earth you would see a small blue ball next to a vertical yellow wall. I also have some recollections of the insides of planets where you could see the core, mantle etc. Most significantly there was a kind of minigame in the program where you attempted to shoot a satelite,spacehip into orbit around a planet or something. If you did it wrong then the object would either fly off the screen, or crash into the planet. I guess it is more or less from the 486 era. I'm pretty sure it was in 256 colours.

Does anyone have any clue as to what this could be? I just thought of it the other day, perhaps for the first time in almost 20 years and I would really like to see it again.

Aha found it! : Its Discover Space. Its quite good actually and can be downloaded from myabandonware