A collaborative study between scientists from the United States and China delves into the implications of the theory of primordial black holes, those that would have been born in the first moments of the universe and that would not be the result of the collapse of massive stars. Given their origin, primordial black holes are not subject to any set size. If they exist, researchers are justified in “thinking outside the box” to find them.
The theory of primordial black holes, level 1
Although it sounds implausible at times, the theory of primordial black holes has been on the minds of astrophysicists for decades. The general idea is that during the first second after the Big Bang, matter became so concentrated in some regions that black holes of all sizes immediately emerged.
The concept of black holes born together with the Big Bang is attractive to physicists because these structures can have dimensions of several hundred kilometers, but also sizes similar to those of a subatomic particle. This means that in the universe there are small and undetectable points (on cosmic scales) that increase the amount of matter in a specific region. Enthusiasts of the theory think that dark matter, that class of unknown particle that comprises 70% of the total matter in the universe, and primordial black holes are, in fact, the same.
Unlike supermassive black holes, there are no clear traces of primordial black holes. There are clues that allow us to infer its existence, such as the appearance of unexplained gravitational lenses or certain gravitational waves, but nothing is confirmed. For now, the challenge for astrophysicists studying the theory is to find the signatures of these phenomena to finally be able to quantify them.
Where are there primordial black holes?
Two scientists from the University at Buffalo and National Dong Hwa University developed some foundations for the study of primordial black holes. In October, they presented previews of their research. They found that hollow planets and asteroids with black holes in their cores are likely to exist. Small gravitational objects could become “seeds” of planets and later evolve into “shell” bodies. The calculated limit of a planet that can host a black hole is one-tenth the radius of the Earth. If he surpassed it, he would collapse in on himself.
In the case of microscopic black holes, scientists explain that these would leave straight tunnels in conventional materials such as rocks, metals and glass. Even if it were the size of an atom, a black hole would still have the mass of a mountain. Therefore, materials crossed by one of them at considerable speed should present detectable fingerprints. According to researchers, the probability that a rock on Earth will be penetrated by a primordial black hole in a period of 1,000 million years is 0.000001.
“The chances of finding these signatures are small, but searching for them would not require many resources and the potential reward – the first evidence of a primordial black hole – would be immense. “We have to think outside the box because what has been done to find primordial black holes before has not worked,” explained Dejan Stojkovic, co-author of the study. His article will be published in December in the magazine Physics of the Dark Universe.
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