[Kamog]

I experimented some more to try the remote nebula-creation trick.

OK, your nebula-creation ship has to be sitting at a star in a neighboring system to the one you want to destroy. Then you order your ship to warp to the target system and then create the nebula. The ship has to end up somewhere in the target system but it doesn't have to be in the same sector as the star. Of course your nebula ship will be destroyed when the system is destroyed. This works. So your opponent could have a huge fleet parked over their star and you can blow them up without fighting them.

However, if there's a sphereworld in the target system but no star, this trick doesn't work. You can still issue the order, but when your nebula ship arrives in the target system you get a message that says you can't create a nebula because there is no star.

So I don't think you can use this method to create new asteroids where none existed before.