Why is science bent on proving the existence of primordial black holes?

After years, astronomers' quest to prove the existence of primordial black holes (ANP) continues. Indeed, the passage of the years has led us to discover countless new black holes in our galaxy and also in the surrounding areas. However, ANPs are still just a theory without proof. But if they do, they could help us explain how elusive dark matter works.

Research that seeks to achieve these tests in the future published its first issue recently in Physical Review Letters. Within this, the authors Alexander Kusenko, Misao Sasaki, Sunao Sugiyama, Masahiro Takada, Volodymyr Takhistov and Edoardo Vitagliano presented the mathematical development that supports the realization of a physical study.

With this as a basis, they have already started the search for signals from the ANPs using a giant 8.2-meter telescope. Thanks to this collaboration between physicists from the University of California (United States) and the Kavli Institute for the Physics and Mathematics of the Universe (Japan), we could get closer to a better understanding of the formation and original distribution of our universe.

Glimpses of other universes?

According to the theory presented by the researchers, primordial black holes could be evidence of the existence of other universes whose formation occurred mere seconds after the appearance of our own.

Clearly, even if the existence of an ANP is discovered, this would not imply that we would already have a window to parallel realities ready. In fact, we would still be very far from a confirmation of that style.

However, being able to have proof of the presence of primordial black holes could help us understand other mysteries of our own universe, such as the existence of dark matter. Likewise, it would be a key tool to understand the origins of the universe, its galaxies and their arrangement.

As if this were not enough, although it would not give us a simple window to other universes, it could at least indicate the existence of the so-called multiverse. Obviously the latter would still be highly subject to debate and more tests would be required to prove it. However, it would at least serve as a first look at a possible great discovery that would change everything we know about our universe.

What differentiates primordial black holes from the rest?

In other moments we have explained what a black hole is and how they form in space. But, in short, we can say that these are cosmic phenomena in which a star of great mass collapses on itself due to its own gravity and creates what is known as a "singularity".

Within this "singularity" basic laws of physics are broken, such as that two atoms cannot occupy the same space simultaneously, since their masses do not overlap. Inside black holes, this conception breaks down, creating extremely dense spots compared to their volume. In general, this also holds for primordial black holes, just as the strong gravity should be maintained, which does not let even light particles escape.

Now, the ANPs should have a differentiating detail, and this is their own total mass. According to the theory, these should have been created in the first seconds of the universe's existence. Back then, radication would be the queen of space, leaving little room for anything else, and general conditions would be extreme.

Consequently, a lower level of mass and gravitational pressure would be required for a black hole to still be created. For the researchers, this could indicate that ANPs are naturally “smaller” than common black holes, which has prevented them from becoming impossible to detect even now.

Science still hopes to locate a primordial black hole

By this time, black holes have been discovered near the Earth, a supermassive one was located in the middle of the Milky Way as well as other equal ones in the center of more nearby galaxies. However, the issue of black holes remains highly debated, even having nascent trends that still refute them in concept.

For this reason, talking about primordial black holes becomes difficult, since they do not even have the evidence that supports the regular ones. As if that were not enough, due to its small size and long age, it is believed that phenomena such as Hawking's radiation bursts could have made many disappear.

In general, it is considered that, if there were any in our universe, by now we would have already seen at least one piece of evidence. However, the researchers claim that the lack of these may be due to a flawed search process.

A new experiment could help prove the existence of ANPs

In order to finally check whether or not there is a primordial black hole between our galaxy and another nearby one (Andromeda), the researchers hope to observe the border between them through the Hyper Suprime-Cam of the Subaru Telescope.

On previous occasions, this space was tracked for 7 hours and 200 snapshots were taken. Unfortunately, the team that conducted that research did not come up with any evidence to support primordial black holes.

Now, the new proposal is to multiply the observation time and take it to at least 88 continuous hours. According to his calculations, this new longer time span would increase the chances of identifying an ANP at the border between galaxies.

If we do, with the new information we could better understand what is behind the mysterious dark matter. Likewise, we would have the possibility of taking a look from another perspective at the distribution process of the heavy elements of the universe. And, as if that were not enough, it would give us the foot to study the possible existence of other universes parallel to ours.

Reference: Exploring Primordial Black Holes from the Multiverse with Optical Telescopes: https://doi.org/10.1103/PhysRevLett.125.181304