What are the three candidates for 'dark matter' that has remained undiscovered for decades?
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It has been about 90 years since the existence of dark matter as an invisible substance was suggested in the 1930s, but its true nature remains a mystery to date. Various studies have yielded several candidates, and news site Salon.com has compiled three of the most important ones based on interviews with experts.
Why dark matter's mysteries persist after decades of searching | Salon.com
https://www.salon.com/2024/12/26/why-dark-matters-mysteries-persist-after-decades-of-searching/
In 1933, Swiss astronomer Fritz Zwicky suggested that a 'missing mass ' was necessary to explain the behavior of galaxies in clusters, and he called such a mass the In the 1970s, American astronomer Vera Rubin and her colleagues discovered that stars in the periphery of the galaxy were rotating faster than expected, and they named the resulting material 'dark matter.' We have demonstrated the existence of matter.
Since then, various researchers have investigated the true nature of dark matter, and have discovered that dark matter makes up about 26.8% of the universe, and that when galaxies collide, the dark matter contained in the galaxies passes through without slowing down. It has become clear that this is continuing.
It turns out that 'dark matter' has been separated from normal matter due to the collision of galaxy clusters, and the speed difference between dark matter and normal matter is observed for the first time - GIGAZINE
The clues gathered in this way form the basis for designing experiments to detect dark matter, the most popular of which is whether dark matter is made up of ' weakly interacting massive particles' (WIMPs) . One is to confirm it, and the other is to search for a hypothetical elementary particle called the axion .
Candidate 1: WIMP
At the Gran Sasso National Laboratory in Italy, the world's largest underground laboratory, researchers are searching for dark matter using detectors filled with liquid xenon.
Dark matter is invisible to the naked eye because it does not interact with light, but the aim of this experiment is to detect it by detecting the extremely faint light emitted when it collides with xenon particles. .
According to Dr Abigail Kopec of Bucknell University, who is involved in the experiment, they expect about one billion WIMPs to pass through the detector every second. But so far, they have not seen any particle collisions. It has not been confirmed.
WIMP is based on the theory of supersymmetry, which says that all particles we know, that is, the elementary particles of the Standard Model, must have a partner particle. The properties of dark matter in the universe match those of dark matter, and it has been hoped that these could be WIMPs. More than 10 years of observations and experiments with the Large Hadron Collider (LHC) have provided no evidence to support their existence. was not obtained.
by Chic Bee
'The idea has fallen out of favor because we haven't found any evidence of supersymmetry using the LHC,' said Tracey Slattier, a theoretical particle physicist at the Massachusetts Institute of Technology. 'It still has promise, but the LHC is a long way from now.' 'The misfire made scientists realize that this might not be the only possibility.'
Candidate 2: Axion
Another candidate, the axion, is a particle proposed in quantum chromodynamics (QCD) that suggests that dark matter is far lighter than any particle discovered so far and behaves like a wave. is.
The discovery of the axion is attractive to scientists because it could help resolve the ' strong CP problem ' in the standard cosmological model, said Ciaran O'Hare, a particle astrophysicist who studies dark matter at the University of Sydney. That's the theory.
'If dark matter is QCD axions, then it's essentially invisible, so we wouldn't know we were swimming in it, so we'd need some very special experiments to find out,' O'Hare told Salon.com. We will need to do that.'
For example, the University of Washington is conducting an experimental project called ADMX (Axion Dark Matter eXperiment) using an axion detector.
Successfully developed the latest equipment to detect the mysterious particle 'axion' that may be the true identity of dark matter - GIGAZINE
by NASA Goddard Space Flight Center
Scientists have also already discovered neutrinos, particles with very little mass like the axion, which are sometimes referred to as a type of ' hot dark matter ' because of their high speed and energy. However, these particles are too light to explain the behavior of dark matter in the universe, and so they are not thought to make up much of it, at least.
Candidate 3: Primordial black hole
Apart from elusive particles, another popular candidate is the primordial black hole , which was born shortly after the Big Bang.
If we could observe a black hole the size of an asteroid, it would be strong evidence of a primordial black hole, but discovering a small black hole, which does not emit any light, is quite a challenge.
'It's incredibly difficult to observe an asteroid-mass black hole, so it's going to take some time to bring the ideas for the search technology to fruition,' O'Hare said. 'With any luck, we'll get past that hurdle by around 2030.' 'I believe that we will be able to clear this hurdle and observe primordial black holes, or even eliminate black holes as candidates for dark matter.'
Astronomers have already discovered several potential 'Hawking stars' that could house primordial black holes, and are investigating what these would look like if they were present.
Research results show that 'primordial black holes' that existed immediately after the Big Bang are devouring stars from the inside - GIGAZINE
In the field of dark matter research, numerous experiments and observations have been carried out to date, but none have led to the discovery of dark matter. However, even failed attempts are an important step in coming closer to the true nature of dark matter. There is no difference. Many experts are optimistic that we will be able to understand the true nature of dark matter within 10 years from the time of writing. Or, we may find that dark matter does not exist . This could potentially lead to the discovery of entirely new, previously unknown physical laws.
'The idea of experimentally testing dark matter may just be a false hope,' Slattier said. 'But given what we know, dark matter is not a particle that we know of. It's possible that these new particles, lighter than the Sun, are being produced all around us all the time and flying around in our rooms. If so, we should be able to find them just by placing a sensitive detector in the room. 'Yes,' he said.
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