A story came out a couple of years ago, a real story, that scientists had been picking up mysterious repeating radio signals from space. No one really knew what it was, or its precise point of origin. The debate continues for what might be causing these signals.
If you needed a plot hook for your game, this is it. You’ve identified mysterious signals from space. What do you do? Investigate? Prepare for invasion? Prepare for diplomatic missions? Work to develop greater technology (meaning seeking out knowledge and resources?) The scope of the game is wide open.
Then there are things to consider like, level of technology. Has science achieved interstellar travel? What kinds of communication is possible? Could humans “read” the transmissions, and beam their own back?
I love the idea of deep space communication, and the possibility of contact with another sentient life form. For gaming, the possibility for some kind of confrontation is clear, but it is wide open for the players. Take the game where you want and just go for it.