From time immemorial, human beings have wanted to explain the most unpredictable and disturbing phenomena in the universe. Although the study of astronomy is a constant in all civilizations, astronomical events of a more “unpredictable” nature, such as comets or eclipses, are considered “omens of misfortune” and / or “actions of the gods.”
The fall of Saxon King Harold II in 1066, during the Norman invasion of William the Conqueror, was attributed to the bad omen of the comet’s passage (later named “Halley”). And during the battle of Simancas (Valladolid, Spain) between the armies of Leon Ramiro II and Caliph Ad al-Rahman in 939, a total solar eclipse caused panic among the armies on both sides, postponing the battle for a few days.
How, then, would our ancestors react to the existence in the universe of objects — so-called black holes — capable of absorbing everything that enters them, including light?
While the biggest black holes have already been discovered and even photographed, there is now possible evidence – as shown in my recent study for small black holes the size of potassium atoms (with a radius of about 0,23 nanometersequivalent to 0.23 billion per meter). These atomic-sized black holes formed in the early moments of the Big Bang may even contain the set of dark matter of the universe.
In 2019, cooperation from eight radio telescopes located in different parts of the world managed to take the first picture of a giant black hole (6.5 billion times more massive than our Sun). It is located about 55 million light-years from us (a light-year corresponding to a distance of about 9.5 trillion kilometers) in the center of the galaxy Messier 87.
Italics of the word photo It’s no coincidence: how can a picture be taken of an object that captures light and therefore could not be seen by cameras that use light to create a picture? The answer is simple: we do not observe the object itself, but the remnants of a star that are swallowed by these black holes.
This stellar matter rotates at enormous speeds around the black hole, and its brightness can be detected when it reaches temperatures of the order of a million degrees Celsius. The disk of matter that surrounds the black hole is called the “accretion disk” and is considered the edge of the black hole – once passed, nothing can escape, something we call event horizon.
In the image above you can see the accretion disk and the event horizon of the black hole located in M87.
Primary black holes
Significant parts of the black holes in the universe are formed by the gravitational collapse of the stars, consuming all their fuel in their final stage: they are called “stellar black holes”. Not all stars will turn into black holes at the end of their lives; when the core of a star is less than two or three solar masses, a stellar black hole cannot be created.
That is, there is a minimum stellar mass below which the star cannot collapse into a black hole. As an example, our Sun will never turn into a black hole at the end of its life, but other massive stars like it. the red supergiant Betelgeuse they will inevitably become black holes.
There are other black holes called “primitive” or “primary” black holes, which, as their name suggests, were created in the early days of the Big Bang, when the universe first began, and could theoretically have any mass. They can vary in size from a subatomic particle to several hundred kilometers.
And when it comes to black holes, supermassive ones emit virtually no radiation, while the smallest ones emit the most radiation. But how is this phenomenon possible: supermassive black holes that emit virtually no radiation and capture everything, even light?
The answer was provided by physicist Stephen Hawking in the mid-1970s. He postulated that quantum effects near the event horizon of a black hole could cause the emission of particles that could escape from it. That is, black holes that do not accumulate mass in any other way will they gradually lose their mass and eventually evaporate.
This Hawking radiation is more evident in low-mass black holes: the evaporation time of a supermassive black hole with a million solar masses is 36×10 to 91 seconds (much longer than the current age of the universe).
On the other hand, a black hole with a mass equivalent to a ship of 1000 tons will evaporate in about 46 seconds.
In the final stages of black hole evaporation, they would explode and generate a huge amount of gamma rays (radiation even more intense than X-rays).
Capture an atomic-sized primary black hole
So how can atomic-sized holes be proven before they evaporate completely?
In a recent study from atomic-sized black holes, an astrophysical scenario is proposed in which one of these small black holes is captured by a supermassive one. As the atomic-sized black hole approaches the supermassive event horizon, the fraction of Hawking radiation that can be detected from Earth gradually decreases until it reaches the size of a beam of light.
The following animation shows the above process in more detail.
This beam is compatible with thermal gamma rays (GRBs) already measured in astronomical observatories. It is these GRBs that are experimental evidence of such small black holes that are serious candidates for the dark matter of a still unexplored and conquering universe.