The legends said they loom silently in the darkest depths of outer space. Growing. Accreting. Devouring. Grandpappy Einstein would spin mathematical yarns about collapsed stars so dense not even light could break free from their inescapable grasp, but he never really believed the stories were true. “Now don’t fret,” he’d conclude, bouncing the cosmological community on his knee. “The material within would have to reach orbital velocities equal to the speed of light, and we all know that can’t happen. Black holes aren’t real.”
He was wrong. Dead wrong. Now we estimate there must be around 100 million of the ebon annihilators in our galaxy alone. And the biggest, baddest mofo of them all lies right in the center, snacking on asteroids while we all helplessly circle it. But that’s 26,000 light years away. And the closest stellar-size black hole isn’t any nearer than 1,500 light years. They can’t possibly hurt us way out here, right? Wrong again, chump! Even if you don’t get close enough to be torn apart like a piece of spaghetti by the black hole’s gravity gradient, the monsters can still find ways to reach out and wreck your shit!
The very birth of a black hole could ironically kill many of us. The little-understood phenomenon of gamma ray bursts (GRB) are thought to result from the implosion of a rapidly rotating, high mass star, which leads to the creation of neutron stars or black holes. Gamma rays are the most energetic of all electromagnetic radiation, even more potent than X-rays, and the giant blasts emitted by black hole-birthing supernovae are the brightest events in the universe. If a star within 10,000 light years of us went pop, a directed GRB could fry off up to a quarter of the Earth’s ozone layer, leaving us underprotected from harmful solar emissions, causing extinctions and radiation sickness.
The supermassive black hole at the center of our galaxy formed long ago, so it’ll have to take a different tact if it wants to strike at us. Maybe it’ll just start chucking stars our way. As of 2012, 16 so-called “hypervelocity stars” had been identified in the Milky Way, zooming through at 2 million miles per hour, and six as big as our sun have been newly discovered. The solar speed demons are presumed to have been slingshotted away from Sagittarius A* when the block hole greedily gobbled their companion stars. Needless to say, if one of those nuclear-powered projectiles was flung in our direction, the immediate effects would impact more than just the atmosphere.
And if that doesn’t work, hell, maybe it’ll just come for us itself! NASA announced last year they had identified what seemed to be a supermassive black hole being ejected at high speed from its host galaxy. Astronomers suggest that when the galaxy collided with another, the two black holes at their respective centers also merged, creating titanic gravitational waves that kicked the new super-entity out of the neighborhood. A body bearing down on us with a mass millions of times that of the Sun is… literally unimaginable.
WHAT DOES THIS MEAN?
Fortunately, we don’t have to spend a lot of time imagining these things. While they could and perhaps should make for great science fiction fodder, the likelihood of any of the aforementioned disasters occurring is essentially nil. A gamma ray burst, emanating only from two opposing ends of a supernova, would have to be pointed directly at us to have a devastating effect, and a GRB close enough to cause significant damage is only thought to happen every 5 million years or so. Warren Brown of the Harvard-Smithsonian Center for Astrophysics thinks that there lurks only one hypervelocity star for every 100 million ordinary ones. The Milky Way’s supermassive black hole shouldn’t be able to go mobile until we collide with the oncoming Andromeda galaxy in 4 billion years. Black holes do have tantalizingly destructive consequences, but they’re unlikely to bother us in the near term.
That goes for the theorized “micro black holes,” too. Some predictions expect that tiny versions of the beasts may have existed shortly after the Big Bang, and more far-out ponderings wondered if they could also be created by the Large Hadron Collider in Switzerland. It hasn’t happened, as far as we know, and even if it did, the microscopic miscreants would evaporate before they could do any damage. It may be fantastic to think about, but on the list of potential cosmic catastrophes, black hole destruction should fall far behind things like asteroid impact, which could be more easily avoided if predicted ahead of time.