As much as I would like for it to be aliens, I think even a 1% belief that it's aliens is privileging the hypothesis too much. Previous 'weird' cosmological objects have all turned out to have far more plausible natural explanations.
All this said, though, it does seem kind of natural for a civilization to put most of its effort into surviving in its own solar system - where energy is plentiful and communication is rapid - rather than spreading outward into tenuous space where the chances of survival are very low. It's not obvious to me why a civilization should choose to colonize other solar systems. That said, if a civilization chose to do that and was successful in doing that, it would quickly become very populous, but it requires an initial impetus.
But how often does that have to happen? They only looked at about 150,000 stars. There are hundreds of billions in our galaxy alone, and if alien civilization developed even 1% earlier than ours, they'd have had time to colonize the entire Virgo supercluster, so long as they start near the center.
If it's worth saying, but not worth its own post (even in Discussion), then it goes here.
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