SM mode doesn´t show any computer controled races in the "Select Default Race" menue, you would need to enter designer mode, for which you also need the password from Steve.
Other than that, I am at a loss.
Now, Aurora creates a new jump point in a system, when a newly generated jump link connects to an already surveyed system (this is called a hidden jump point), but I am assuming you did your second grav-survey after the first alien ships showed up, so this can´t be it.
Hm, come to think about it, in Starfire (the roots of Aurora), hidden warp points (from the hidden side) can only be discovered by observing a ship coming through, perhaps Steve has put something similar into Aurora?