Dark matter is a mysterious substance that fills the universe, and the amount of which is five times the amount of ordinary matter. Huge clusters of dark matter have already been discovered in various galaxies, but, according to existing theories, clusters of much smaller sizes, but having a sufficiently high density, should form from dark matter. Recently, during observations made using the Hubble Space Telescope, scientists obtained evidence of the existence of small clusters of dark matter, which, in turn, served as evidence of a number of relevant theories and hypotheses.
The concept of dark matter arose after astronomers in the 1930s noticed that some galaxies move in a way that assumes they have much more mass than the mass of actually observed matter. And this missing mass must be accounted for by some invisible substance, which was called dark matter.
However, the search for dark matter turned out to be a very difficult task, since it interacts with ordinary matter only through gravitational forces. Dark matter cannot be seen, felt, tasted or smelled. We can only see the effects of its gravitational influence on the environment, which played a huge role in the process of formation and development of the Universe.
In areas of sufficiently large and dense clusters of dark matter, powerful gravitational forces arise that attract ordinary matter to themselves. And quite often, as a result of this process, new planets appear, young stars light up, from which galaxies and even larger cosmic objects – clusters of galaxies are formed.
The version of the formation and development of the Universe described above to the form in which it exists now is considered to be the most correct and generally accepted. According to this theory, dark matter is cold, i.e. its particles move relatively slowly and there are no fast processes in its environment. As mentioned above, scientists have already obtained evidence of the existence of huge dense clouds of dark matter in galaxies. But until recently there weren’t even any hints of the existence of small “clumps” of dark matter, although the theory admits this.
Thanks to observations made with the Hubble Space Telescope, scientists from NASA’s Jet Propulsion Laboratory (JPL) and the University of California at Los Angeles discovered small clusters of dark matter with a mass approximately equal to that of a passenger airliner.
“Dark matter contained in such small clusters is colder than previously thought,” the researchers write, “Astronomers have already made quite a lot of observations aimed at searching and studying dark matter, but only we were able to attest to the presence of small ones.” blocks of “very cold dark matter. And this was done through sophisticated theoretical prediction, static ground-based experiments, and data from the Hubble Space Telescope.”
Scientists during their searches studied eight quasars – bright space objects surrounding massive black holes. These quasars were studied using a well-known method called the gravitational lens. The effect of such a lens occurs when light from a distant object passes by another object with a large mass, which by its gravity changes the trajectory of light, sometimes focusing it like a huge lens. Of course, such gravitational lenses never have a perfect shape, so the image of a distant object turns out to be very distorted and can even be duplicated several times.
In this case, all the quasars under study were located approximately at the same distance from the Earth, which amounted to about 10 billion light-years. And the role of gravitational lenses was performed by large galaxies located at a distance of about 2 billion light years. In most cases, the gravity of galaxies refracted light from quasars so that their images were duplicated at least four times.
Comparing the obtained distorted images of the quasars with what was expected from the point of view of theoretical calculations, scientists were able to find the location and calculate the mass of even the smallest “block” of dark matter located in the path of light flying from the quasar towards the Earth.
“These small “clumps of” dark matter act like the smallest cracks in the body of a gravitational lens created by a galaxy, “the researchers write,” They are responsible for small changes in brightness and a shift in the position of each of the four images of the same quasar. We calculated a theoretical model based on the perfectly smooth shape of the gravitational lens, and by comparing the real data with the data of this model, we were able to determine the position, mass, temperature and some other parameters of even the smallest clusters of dark matter”.
Scientists claim that the results of their research are the first practical confirmation of the theory of cold dark matter. This, in turn, will allow scientists to abandon a number of alternative theories and concentrate on searching and studying only those dark matter candidate particles whose properties fit into the framework of the observed effects.