The display of cards that go in the middle of the table. (This will have available planets and ships to buy)
The System (Evoking solar system obviously, "solar" doesn't really transfer throughout the galaxy though)
If that term is too confusing (it's a pretty popular sci-fi term so it shouldn't be) it could just be the Galactic/Interstellar Market or some such.
The deck pile that those cards come from
I dunno about this one...deck is such a standard. If you want to go with something semi on-theme it could be the Exploration Deck, if you want to be really really on-theme you could do something like The Wormhole, The Unknown, Deepspace, or Terraforming and Innovation. But those all feel like real stretches to me (except maybe Deepspace).
The Trash Pile (Thats not called Trash or Graveyard)
The Void or Black Hole
I'm no sci-fi expert, but I hope these help anyway!