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Paul M. Sutter is an astrophysicist at SUN Stony Brook and the Flatiron Institute, host of “Ask an astronaut” and “Space radio, “and author of”How to die in space. “ Sutter contributed this article to The expert voices of Space.com: Op-Ed & Insights.
Black holes look pretty scary – dark, powerful, eerie. And now astrophysicists have concocted something else: primordial black holes, forged in the first moments of the universe, which flood the current cosmos.
So what are the chances that one of these ancient monsters will come wandering to Earth? An astrophysicist analyzed the numbers.
Related: Swarms of “primordial” black holes could fill our universe
Birth in the Big Bang
The early universe was a wild and complex time. Much different from the gentle-mannered cosmos we inhabit today, the early moments of big Bang were marked by drastic phase transitions, the split of fundamental elements and other wild events. While scientists understand the physics of the first few minutes, what happened before it is shrouded in mystery (and a bunch of complicated math).
You need pretty extreme conditions to train yourself black holes – say, a star collapsing on itself during the last catastrophic moments of its life. The stars weren’t there for the first few seconds of the universe’s existence, but there might have been the right conditions for forging black holes; all you need is a lot of matter or energy crammed into a small enough volume.
In the unknown and unexplored reaches of the distant past of the universe, conditions could have been perfect to flood the universe with primordial black holes, which could have any mass, depending on the conditions under which they were created. But interest in primordial black holes has waned over the decades as research for them has proven to be empty – that is, until we have the Observatory of gravitational waves by laser interferometer (CONNECT).
When LIGO detected its first collision with a black hole, black holes had rather peculiar masses; each was a few dozen solar masses. This mass range is difficult to achieve with standard star-based black hole mergers, as the mergers should be a little too frequent to be plausible). And so, before you even knew it, primordial black holes were back in the spotlight.
A dark encounter
The problem with the processes in the early universe is that if there is some kind of exotic mechanism that can generate black holes, it’s not going to make a few – it’s going to flood the universe with them. In fact, there might be enough primordial black holes traversing the universe to account for at least part of black matter, the mysterious substance that makes up over 80% of all matter in the cosmos.
Let’s say a whole bunch of tiny black holes are invading the cosmos, as a recent article published in the Preprint Database shows. arXiv. What would happen to them?
Fortunately, black holes are not 100% black, and they lose mass through Hawking radiation, the complex quantum mechanical process on the black hole’s event horizon that allows certain particles and radiation to escape. The smaller they are, the faster they lose mass. Black holes less than about 100 million tonnes – slightly lighter than a typical hole asteroid – will lose about half of their mass in the current age of the universe. Because of how Hawking radiation works, black holes larger than this will lose only a small fraction of their mass.
The total number of small black holes in each galaxy depends on how much dark matter you want to explode with them and the size of each. No matter how you cut it, however, there are plenty of them.
And each is fast. Based on computer simulations and observations of galaxy dynamics, dark matter has a speed of over one hundred miles per second. At this speed, an asteroid mass black hole could cover the distance between Jupiter and Earth in just a few weeks. So should we be afraid?
Run numbers
What would happen if an asteroid mass black hole hit Earth? In short, disaster. The black hole would pierce the surface of our planet like a burning knife through butter, but it would immediately begin to slow down due to its gravitational interaction with Earth. Any atom or molecule (or person) crossing the event horizon – the limit of the black hole beyond which nothing, not even light, can escape – would simply move away from the known universe, no longer never be seen again.
In the best-case scenario, the black hole would emerge on the other side of our planet, leaving the survivors to clean up the mess. In the worst case, the black hole would settle in the heart of our planet, where its gravity would be enough to allow the black hole to start feeding. Ultimately, it would devour our entire planet.
Fortunately, according to the article’s calculations, the chances of a black hole settling in the Earth’s core are rather minimal. Black holes are just too fast.
On the other hand, the intersection of our planet with a black hole would lead to another unpleasant reality: heating. As it passes through Earth, the black hole would accumulate matter, and this accretion would generate heat (the same heat that powers active galactic nuclei). The impact of an asteroid mass black hole would end up releasing roughly the same amount of energy as the impact of a mile-wide asteroid.
You know, a dinosaur killer.
Fortunately, black hole collisions are probably rare. In the most “optimistic” scenario – optimistic by scientists’ standards, that is, populating the galaxy with the maximum number of black holes – there could be a collision roughly every billion years, according to the researchers. calculations of the article.
So when it comes to black hole collisions, don’t be too scared.
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