Using 4 straight lines connect these 9 stars together without lifting your pen from the surface. The end of each line must be start of the next line.
Using the information from http://en.wikipedia.org/wiki/Parallel_(geometry)#Extension_to_non-Euclidean_geometry:
- parallel, if they do not intersect in the plane, but have a common limit point at infinity, or [...]
So, if we put this in a non-Euclidean plane, it can be done with one line:
But, of course, this would take forever to draw (But it does pass through the centres of all stars)
I can also confirm it is impossible to do on a Euclidean plane without going outside the box with this Python script.
There are 84 different ways to do it with 5 lines inside the box, but that should be around 11 unique ones because most are reflected or rotated.