A fraction of a second after the Big Bang, long before the first stars and planets appeared, the first celestial bodies may have formed: black holes. The very young universe was filled with opaque, red-hot, high-pressure plasma. That plasma is not evenly distributed everywhere. In the ripples of this primitive soup, the mass may have formed together into a black hole.

The existence of those cosmic black holes follows from the calculations made in the young universe. For nearly fifty years, astronomers around the world have been searching for their tracks. But maybe they were hunting a ghost, and there were never any black holes. Or they may already be too late, and these 14 billion-year-old black holes have long since evaporated. Yet astronomers continue to search. Christian Brinkering, an astronomer at Radboud University, says: “When we find primitive black holes, we look at the oldest personal objects of all time.

Black holes are not holes. Gravity is a strong region but nothing can escape from it. Beyond the event horizon, not even light can escape.

The physics in and around the black holes are confusing and complex. But astronomers have a reasonable understanding of different types of black holes. Astronomers distinguish four categories.

Most black holes are stellar black holes. Stars that are twenty times larger than the Sun are created when they die. Then the outermost layer of the star moves rapidly into a universe with a spectacular explosion, a supernova. The remaining core falls into a black hole. A black hole created in this way can be up to a hundred times the mass of the Sun.

The second group is the giant black holes. There is such a variation in the middle of almost all galaxies. Sagittarius A * in the center of the Milky Way is about four million times larger than the Sun. M87 * In the Galaxy M87, including in 2019 Symbolic first photo Taken from a black hole, it’s six and a half billion times larger than the Sun. These giant black holes are too large to form from dying stars, such as stellar black holes. Sometimes black holes collide and merge, but even many black holes are not large enough to explain their fusion. The third group, medium black holes, have not yet been identified. In terms of mass, they are between groups one and two.

Burning substance in primitive soup

Then there is the fourth group: primitive black holes, which are formed from matter in primitive soup.

Belarusian physicist Yakov Borisovich Zeldovich and Russian astronomer Igor Dimitrovich Novikov began thinking about the origin of primitive black holes in 1966. A few years later, the British physicist Stephen Hawking further developed the theory and mathematics. The idea is that in smaller and larger universes, matter is more visibly packed, and in some places the pressure is greater to make small areas black holes.

Hawking estimates that the mass of primitive black holes ranges from 0.02 mg to 1,000 times that of the Sun. According to Hawking and his Canadian colleague Don Page, a cubic light year should have two hundred primitive black holes (one light year is the distance light travels in a year), they wrote in 1977. It’s not that much, but in the vicinity of the Milky Way, the amount of matter around the galaxy is now about a million times larger. In that case, Hawking calculated that the nearest primitive black hole to Pluto would be much farther away from Earth. Pluto is 40 times farther away than the Sun.

“Anyone who rewinds time in your mind will quickly understand the basic premise of Hawking’s theory that it is reliable,” says Brinkering. Even now we can see the density differences around us: if everything were evenly distributed, dust, for example, would not be able to converge on stars and planets. If you rewind the universe with all its clamps at a time when everything is very dense, the matter in the solid region will be pressed very strongly, where black holes must have formed. Modern computer models, much more advanced than Hawking’s time, still confirm it today. “

But if primitive black holes are likely to exist and they are relatively densely populated around the Milky Way, why have they not yet been discovered? Anupam Masumdar, a theoretical physicist at the University of Groningen: they are hard to find. The only way to actually distinguish primitive black holes from other living things is by mass. We are looking for primitive black holes with different masses than stars. It is a small bandwidth. Only black holes lighter than the Sun can ensure that they are not stellar black holes.

Dissociated particles

But the mass of primitive black holes began precisely in uncertainty. Although some are formed with a mass less than that of the Sun, they can grow by absorbing matter from the environment or merging with other black holes in fourteen billion years.

Another problem is that primitive black holes may have been very light and then disappeared through ‘evaporation’. Because a black hole will evaporate. It works almost like this. In the universe, the particle pairs of a particle and its antiparticle can occur locally. Usually these two particles quickly cancel each other out and ‘eliminate’ them. But they can be disconnected near the black hole. When the particle is too close to the black hole and the antiparticle is absent, the particle disappears into the black hole. The energy from the black hole is thrown into the antiparticle universe at the expense of energy. The escape of energy in the form of particles from a black hole is called Hawking radiation. The weight of the black holes decreases and they evaporate faster. Hawking estimated that it was a primitive black hole weighing more than 10 lbs¹¹ (Ten with eleven zeros) kilograms are now completely evaporated.

In 1974, physicists discovered the theory introduced by Hawking. Previously, it was always thought that nothing could escape once absorbed into a black hole. This is also true to a large extent. Only at the smallest particle size, Hawking found a way.

We can say nothing about their existence until we find them

Sumedha Biswas Astronomer

From Nijmegan, Sumedha Biswas, an astronomer at Radboud University, searches for pristine black holes. She hopes to find their tracks in the waves that form when two black holes collide. “There is a good chance that primitive black holes will form, but we will not be able to say anything definite about their existence until we find them.” The waves are similar to the waves in a rock-throwing pool, called gravitational waves. These waves are collected by detectors and the mass of colliding black holes can be detected using computer models. Dozens of gravitational waves have already been detected from collisions between black holes. I work with my colleagues on ways to search that database in the waves for clues to collisions between black holes that are lighter than the Sun.

Strange collision

Primal Black Hole hunters rejoiced in 2016 when detectors Ligo and Virgo lifted gravitational waves from a curious collision 1.3 billion years ago – how long it took for the waves to reach Earth. This was not about black holes lighter than the Sun. The collision is said to have been caused by black holes slightly heavier than astronomers expected from stellar black holes, but this corresponds to the mass of a larger primitive black hole.

“But this is not yet hard evidence for the existence of primitive black holes,” Biswas said. “The melting of stellar black holes may explain the mass.”

The search for the survival of primitive black holes touches on large open problems. The first is the problem of one of the most sought after particles in the universe; Dark matter. 27% of the universe is made up of dark matter, and no one knows what it is. It betrays itself with a mass that affects its environment. Suitable candidates are small primitive black holes, Hawking suggested, because like black holes, black holes do not emit light, but have mass. Those black holes will not be large: otherwise astronomers will have to see different results.

We know that when a black hole eats too fast, it will explode

Pratika Dayal Expert supermasive black holes

Hawking’s theory became a hit in 2019. Astronomers have observed their telescopes overnight in the Andromeda Galaxy, a spiral galaxy 2.6 million light-years away. There they searched for extraordinarily bright stars caused by light curving beyond the black holes. They tested Hawking’s theory for primitive black holes with a mass of one billion to a hundred thousand times that of the Sun. According to Hawking, they found less “clarity” than there was.

Brinkering from Nijmegan: „It is not yet one hundred percent excluded, you can do the same tests with small mass black holes. But by avoiding masses, dark matter is less likely to be formed by small black holes.

The second conundrum that primitive black holes can solve is supermassive black holes. Ancient black holes, unlike stellar black holes, have plenty of time to grow: until the universe is old. It only happens when they are in the center of the galaxy, where they can absorb enough matter and the black holes needed to merge.

Early universe

But trying to bring the current strong black holes back to the primitive black holes quickly becomes a problem, says defendant Dayal. He specializes in supermassive black holes at the University of Groningen. “For a black hole to grow so large, it must eat fast. When a black hole eats too fast, we know it ‘explodes’: that is, it pushes matter into the universe around it. Even the fact that black holes are the seeds of giant black holes remains a mystery.

Biswas from Nijmegan: “Once the primitive black holes are discovered, their mass and number are sure to tell us something about what the primitive universe was like.”

Astronomers can never find them, while they expect them based on current knowledge. They may not be the only theoretical celestial objects that have ever been proven, and some expected galaxies, for example, have never been discovered. If the existence of primitive black holes has never been proven, what about the theory of conditions in a very small universe? Brinkering: “If there is no indication of the existence of primitive black holes, then there is something wrong with our understanding of black holes or their origin.”

Illustrations Jasmine van der Waide