Broadcasts of patterned radio noise being blared into the universe are mistaken for Space Whale mating calls causing hordes of sexually frustrated Whales to "beach" themselves towards the source of the signal like moths flying into a lightbulb but with more apocalyptic dinosaur-killer asteroid-ishness. Incidentally, this is the explanation behind the fermi paradox as any planetbound species which starts using radio inevitably gets themselves killed by kamikaze cetaceans.Also, is that a Niven Ring megastructure in the background?