Have you ever had that horror-movie feeling (minus the ominous music) that something was stalking you—except the fog was so thick or the night so impenetrable, even if you swore on the Necronomicon that something which may or may not have poison saliva and multiple rows of teeth was literally exhaling swamp breath on the back of your neck, no one would believe it?
Enter the Great Attractor.
It’s pretty much the galactic Thing That Must Not Be Named. Since astronomers first felt this gravitational anomaly creeping up on the Milky Way, the Great Attractor has been one of the scariest mysteries lurking in the shadows of space—mostly because it was a mystery. Not that it’s much less of one now. Whatever proverbial flashlight our telescopes and satellites have been able to shine on this menacing mass has either been obscured by other galaxies or deflected by space junk. Whatever it hides behind makes the invisible threat seem even more monstrous. But just what is this thing, and should earthlings be afraid?
The only way we can prove the existence of the Great Attractor is from evidence it leaves behind. It is slowly crawling out of the depths of the Laniakea Supercluster and toward the Shapley Supercluster in our backyard. Telescopes haven’t been able to get an eyeful of it until fairly recently because the the Milky way is in the way, and our galaxy is littered with space junk. What we’ve been able to illuminate in the sea of darkness it inhabits is that this cosmic Cthulhu, tens of thousands of times more immense than the Milky Way and seemingly scary enough that astronomers call its lair the Zone of Avoidance, affects the motion of galaxies and star clusters by drawing them and every celestial object within its grasp (a radius of up to hundreds of millions of light-years) ever closer to it. The only monster that can reach its tentacles over such vast expanses of the universe is a gargantuan blob of gravity.
You don’t need to a math prodigy or an android to figure out that our galaxy, which is about 520 million light-years from Laniakea and 650 light-years away from Shapley, falls within the realm of celestial clusters that could theoretically fall into a danse macabre with this gravitational ghost. The question is whether we’re actually caught in the excruciatingly slow process of being dragged towards a chasm of crushing gravity.
The Thing From Outer Space is creeping closer and closer to the Shapley cluster in the Centaurus galaxy. Celestial bodies floating in the universe usually expand with it, but there are so many in this cluster that their gravitational interactions keep pulling them closer together. Even our own cluster is undergoing this phenomenon. Gravity will pull our clique of nearby galaxies uncomfortably close until the Milky Way and Andromeda get into the most epic catfight in the universe. The Great Attractor is likely to turn up the gravity when it invades Shapley, and eventually the Milky Way—and it more than creeps among the stars. Astronomers first shed light on it after mapping the Cosmic Microwave Background, which sounds more like a TV dinner than an investigation of the cosmos. The slightest aberration in space temperature tipped them off to something huge and invisible hurtling through space the at 370 miles per second. How it got to racing through galaxies is still beyond science. If this thing is flying in our general direction at such a high velocity, the Milky Way’s future looks grim. Or not.
Even if our galaxy had a horoscope, it wouldn’t read “certain death” for several billion years. While the Great Attractor would theoretically smash the Milky Way if it kept travelling at the same velocity until it had us as its prey, it would have to do so in one piece. The monster will likely meet its end when one of the superclusters it passes through inevitably collapses and dismembers it. We probably have a greater chance of a zombie apocalypse than a gravitational one.