Where did the idea for dark matter come from?
There are two interrelated quantities in astronomy: the speed of an object in orbit and the mass of the object around which it orbits. When researchers in the 20th century learned to determine the mass of all the stars in the galaxy, they realized that they were orbiting the galactic center incorrectly. The edges of the spiral are moving much faster than they should, as if, among other things, they are influenced by an invisible mass scattered around the visible part of the galaxy. Moreover, the mass of this unknown matter must be much greater than the total mass of the stars. This was not an observational error because it was confirmed by other methods. For example, the mass of a distant galaxy can be estimated by the way it bends light rays due to gravitational lensing. Such calculations also showed the existence of hidden mass, and over time it came to be called dark matter.
It was originally just an abstract concept, referring to the unknown invisible material that makes up most of the galaxy’s matter. Many astronomers thought these were perhaps faint but recognizable objects like brown dwarfs, neutron stars or black holes. However, as scientists accumulated knowledge, they realized more clearly that this was impossible. Therefore, today’s dominant theory is that dark matter consists of unknown types of particles that have only mass and gravity and do not interact much with light (and ordinary matter in general).
Is it possible to see the invisible?
Understanding what these particles are is one of the most important tasks of modern science, the job of theoretical physicists. There are many approaches to their study, but generally it involves making assumptions about the properties of these particles based on these properties, modeling the behavior, and comparing this to what we observe in the Universe.
In its crudest form, the properties of these particles can be understood using simple logical reasoning. Let’s imagine that there is mass. The mass of an elementary particle is its defining property A single dark matter particle is comparable to the mass of a star. In this case, all star clusters are torn apart due to gravity as they move through the galaxy, but star clusters remain. This means that their mass is significantly lower than that of the Sun.
The lower limit of the mass of these particles can be calculated in a similar way. Quantum particles are subject to the uncertainty principle; In particular, they do not have a clear location in space and are more like a cloud. The smaller the mass, the larger the cloud, and ultimately the size of this cloud can be so large that it does not fit into the galaxy – and we know that dark matter is tightly bound to them. The accuracy of the coordinates may be higher, but at the expense of increased uncertainty in the speed of movement. If this uncertainty reaches a speed greater than 30 km/s, the particles will overcome the gravitational pull of the dwarf galaxies and fly out of them. (Stars orbit around the center of the galaxy like dark matter particles). With these two constraints, physicists calculated that the mass of dark matter particles must be greater than 10.-22 eV is 27 times smaller than the electron mass.
What is the latest discovery?
Upper and lower limits of mass Russian scientists from the Institute of Nuclear Research of the Russian Academy of Sciences carried out a series of simulations on a supercomputer of the behavior of dark matter particles in the galaxy. Simply put, we can say that they are interested in “ultralight” (particle mass 10).-22 eV) and “only light” matter (10-5 eV, 10 times less than the electron mass).
As a result, physicists reached an unexpected conclusion: It turns out that such dark matter accumulations can form Bose-Einstein condensates. This is the name given to the state of matter cooled to almost absolute zero, where a large number of atoms have the lowest possible energy. In other words, the thermal motion of the atoms stops and they freeze, leading to physical effects such as superfluidity. The fact of this discovery is surprising to physicists: it was believed that atoms enter Bose-Einstein condensation due to electromagnetic interaction with each other, and it is impossible to achieve the same effect using gravity alone.
How does such dark matter behave?
Such properties of dark matter point to its special behavior in the galaxy. It should contract into round drops, but of an unusual kind. As mentioned above, the smaller the mass of a quantum particle, the larger the size of its cloud. So a drop of light and ultralight dark matter are a lot of fuzzy clouds that lie within each other and do not “interfere” with each other.
The most interesting results were shown by modeling the behavior of “only light” dark matter (10-5 house). In the galaxy, many small clusters (clouds), similar to stars, should form, each with a total mass like that of a large asteroid. These clusters, about the size of Earth’s orbit, fly around the galaxy and slowly aggregate into droplets of Bose condensate.
“INSIDE article In 2018 we proved the fact that only dark matter in the cloud must coalesce into drops. This was of no interest to anyone because astronomers could not detect small objects. However, end In our research, we found that the droplets grow by absorbing the dark matter flying around and their masses can reach the mass of an asteroid. You can call the enlarged blob a Bose asteroid, but this is my author’s term and is not scientifically acceptable. The diameter of such an object is about 100 km, Dmitry Levkov, senior researcher at INR and one of the authors of the study, told socialbites.ca.
Could a Bose asteroid hit Earth?
Although the matter has been called dark, a Bose asteroid would be completely transparent at every range: to radio waves, to visible light, to X-rays, and even to electron beams. Objects feel solid due to the electromagnetic repulsion between atomic nuclei, but dark matter is incapable (or nearly impossible) of such an interaction. As a result, such an asteroid would be completely intangible and would not even be felt as a gas.
But that doesn’t turn it into the famous Russell teapot.(This is a witty philosophical abstraction – an invisible, abstract teapot that orbits around the Earth, but does not affect anything and there is no need to explain the phenomenon. Therefore, it is pointless to discuss its existence and properties). The Bose asteroid is indeed capable of passing through the Earth like a disembodied soul, but with gravity acting on its own. For example, the moon’s gravity causes water masses in the ocean to shift, causing the Earth to deform slightly. In the case of the Bose asteroid, the details depend on the speed of movement and many other parameters, but it is likely to cause an earthquake.
However, it will not be easy to detect such an object without an earthquake. Theoretically, gravity bends the paths of light rays like a lens, but it is so weak that modern telescopes cannot see it. Another hypothetical method involves observing fast radio bursts. Astronomers regularly detect bursts of radio emissions in the sky lasting a few milliseconds, and there is no clear explanation for this phenomenon.
“In some of our models, the probability that each particle of light dark matter will disappear and decay into two photons is incredibly small. When such particles gather on a Bose asteroid and their numbers are measured in numbers with tens of zeros, even a very small possibility can play a role. One of the particles will decay into photons, which increases the chance of the decay of its neighbors.” “As a result, a chain reaction could occur that would cause a flare exactly in the range where radio bursts are detected. It is worth noting that this hypothesis is considered exotic, and astronomers themselves tend to believe that these flares are caused by magnetars, a special type of neutron stars,” he explained. Levkov.
The work of Russian physicists and their predictions about the properties of dark matter are difficult to test experimentally. But if their simulations turn out to be very close to reality, it will be one of the biggest breakthroughs in 21st century physics.