We have small and giant black holes, but the intermediate ones do not appear. Now some scientists have designed a method to search for them and they already have two candidates

Today astrophysicists have a lot of information about black holes. They have even been photographed. However, there are only two types of black holes for which a multitude of evidence has been found: supermassive black holes, which are colossal in size, and stellar black holes, which are formed by the collapse of a star when it runs out of fuel. Supermassive ones usually have masses between 100,000 and 10,000 million solar masses. The stellar ones are much smaller, with approximately a mass equivalent to that of 3 to 100 suns. So what happens in the intermediate range? Don’t black holes of intermediate mass exist, between 100 and 100,000 solar masses?

This is a question astronomers have been asking for a long time. Theoretically, they could exist, but no evidence has been detected. Now, a team of scientists from Yangtze University in China, has devised a method which could be useful to find them once and for all.

Gravitational microlensing of fast radio bursts. These scientists have used a method that is based on searching for fast radio bursts that have experienced a gravitational microlensing deformation. These deformations are caused by massive objects that stand between the path of the blast and the Earth. By studying the effects of these disturbances, its mass can be calculated.

For this reason, these scientists have analyzed a catalog of these bursts, looking for those that may have been distorted by gravitational microlensing and have been left with two candidates whose mass would correspond to an intermediate black hole. The best? They also fit with primordial black holes, so they could even serve to better understand dark matter.

Clarifying concepts. Now let it be understood. Fast radio bursts are short bursts of radio waves, which come from far away, beyond the Milky Way. There is no consensus on its origin, but many have been detected, it even seems that there are a large number in a single day.

For their part, gravitational microlensing are formed when a very massive object comes between a light source and the Earth. It is so massive that, due to the action of gravity, it doubles space-time and, with it, the path of light that reaches Earth. As a result, multiple and/or magnified images may form. The point is that fast radio bursts themselves can be altered by gravitational microlensing when a very massive object crosses their path.

Gravitational microlensing

Canadian Hydrogen Intensity Mapping Experiment (CHIME). This is a Canadian radio telescope initially designed to map the presence of hydrogen in large fractions of the observable universe. Thanks to its large collecting area and field of vision and its bandwidth, over time it was seen that It was also very useful to detect fast radio bursts. They are very fast, but when observing so much sky at once they do not go unnoticed.

For all this, the authors of the study that has just been published have analyzed the CHIME catalogwith special attention to bursts that at some point have suffered a disturbance by gravitational microlensing.

Two candidates. Of all the distorted bursts they found, there were two whose size matched possible black holes of intermediate size. One had between 539 and 609 solar masses and the other between 1,544 and 2,571 solar masses.

Curiously, there were no galaxies or galactic clusters around it. When black holes form through physically well-known collapse processes, they are usually in the centers of galaxies. However, when they are isolated, as is this case, what is expected is that they are primordial black holes. That is, black holes that formed in the early stages of the Big Bang, before there were even stars that could collapse.

something unexpected. These scientists expected to find intermediate black holes, but they may also have found evidence of the origin of dark matter. One of the hypotheses about this mysterious matter that makes up most of the Universe is that it is partly composed of primordial black holes. The problem is that the existence of primordial black holes has not been proven.

With this new study, two birds could have been killed with one stone: demonstrating that intermediate mass black holes and also primordial black holes exist, in turn helping to unravel the dark matter mystery. Without a doubt, it is a cosmic carom that is worth continuing to investigate.

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