I found this thread really useful; thanks guys! I'd found a couple of nebulae really close to my homeworld, done a ton of scouting, but just couldn't see any more. It seems that the blue wormholes for the nebulae get drawn under anything that might be sitting on top of them, but they don't have a label until you get the champion to go through them, so they're hard to see.
This tip really helps, but perhaps the nebulae wormholes should be made more obvious in some way. I had a few ideas:
1. Make the wormhole graphic bigger, or flashing on top of all other graphics, at least until it's been explored.
2. Show the nebulae on the galaxy map before it's been explored.
3. A note in the top-left saying that there's an unexplored nebula on this planet.
Any thoughts? Or is this obvious enough for most people already?