'We could say: Now we know the size of the universe.'
Live Science, the astrophysicists measured perturbations in the cosmic microwave background , which is sort of like the ambient noise of the cosmos that was given off when the universe began. What they found is that there seems to be a cap on how big those perturbations can get. Unless the researchers made an error, that's an indication that the universe closes in on itself, as an infinitely-open universe would be able to fit CMB perturbations of any size.
The elephant in the room, of course, is the question of what happens when an object reaches the "edge" and loops back around. Unfortunately,notes, that's not actually possible. No matter its shape, the universe is still expanding faster than the speed of light, so no one and nothing could ever travel far enough to test it out.