Polaris is not the locked system. The system in question is called LFT 509. Watch the video from around 6:00 minutes
If you take note that system says it is allied with Federation and has an economy. Yet, there is no obvious station listed in that system - but there must be one for it to have an economy and be allied to a faction. It has a Gas giant with 8 planets, also has an ateriod belt in the system. So the theory is that there is a hidden station orbitating that 8th planet in the locked system, or is located in that asteroid belt. But it's hidden from view unless you get a permit to enter it (that's the test). An invitation from the dark wheel.
Interesting also. The system Shinrarta Dezhra (which is a system you need Elite Rank to enter) is also allied to the faction federation and has a few planet bases in it showing that they are controlled by the Dark Wheel. So even the Federation being the controlling faction of LFT 509 sort of matches up as well.
I think right now that is the
best theory as to where to the Dark Wheel hidden station might be located. It matches a lot of the story. It has an asteroid belt, a gas giant with 8 moons, it's close to Sol inside the bubble. It's a locked system - so you can't gain access to it without passing some test. And interestingly... when they got the data for the other locked systems using the Carrier glitch before it was fixed - all the other locked system data they got did actually show the stations in them present on the map. Yet, LFT 509 doesn't show a station even though the system info indicates there should be a station present in it. That sure makes it seem odd?
As far as the "test" goes for the Dark Wheel. I was thinking about this. So okay, to gain access to a system that has planet bases controlled by the Dark Wheel. You first needed Elite rank to gain access to Shinrarta Dezhra... that has a planet with two bases controlled by the Dark Wheel. So could "maybe" taking missions from one of them bases (controlled by the Dark Wheel faction) result in getting offered the permit for LFT 509. And the first part of the test was to gain access to Shinrarta Dezhra to get to them bases?