Hmm. There are a handful of choices, unless you want to go somewhere and buy an ADS! As Morgan Grimes said above, if there's a Nav beacon in the system you can drop down next to it and scan it to get the full system map. But with the system being largely non-specific other than the crash site I don't know if there's a Nav beacon there. It's not a system I've personally visited.
The second choice is to go old-school on planet detection. Fly away from the star and keep an eye out for points of light moving against the background. These will be planets and if you get close enough even the BDS will be able to pick them up with a honk (as it already did with the nearest planet). The problem is that you're looking for the ninth planet, which is likely to be fairly distant from the star. You could waste a lot of time flying in the wrong direction and never find it.
Third option: wing up with a friend who has the full map and follow them to the crash site.
Fourth option: hang around in Open play and look for another CMDR jumping in and flying off away from the star. Chances are they're headed for the crash site, so either request to wing up or simply tailgate them. There is a risk in Open that other CMDRs may not be friendly, so another option is Mobius if you have access, but obviously the odds of seeing someone else are lower than in Open.
To be honest it'll probably be quicker (assuming there's no Nav beacon) just to fly somewhere and upgrade the scanner. But if you want to role play the situation there are a few ways to go about it.
