Dark matter is one of the most mysterious and, at the same time, important phenomena for astronomy, having been discussed and studied for decades. Recently, researchers at the University of Tokyo announced they had achieved a breakthrough in this field, but some scientists still doubt their conclusions. Portal livescience.com speakWhy.
NASA's Fermi telescope, which specializes in studying light in the high-energy spectrum, has detected the emission of particles associated with dark matter at the center of the Milky Way. That is the opinion of the authors of a scientific work from the University of Tokyo, published in the Journal of Cosmology and Astroparticle Physics. Although this is not the first big announcement made with Fermi, if the authors of this work are correct, this is the first time dark matter has been observed in human history.
For context, dark matter is the substance that experts believe makes up the majority of matter in the universe. Today it can only be tracked by its gravitational influence on other objects. For example, in a 1933 monograph, Swiss astronomer Fritz Zwicky claimed that distant galaxies were moving around each other faster than calculations predicted because the mathematical predictions were based only on visible matter visible through telescopes. So the culprit is most likely dark matter, which does not emit light.
There have been many different theories about dark matter, but today most astronomers tend to believe that it consists of subatomic particles. Therefore, the work of scientists from Tokyo focuses on a popular hypothesis – weakly interacting large particles, or WIMPs.
WIMP goes beyond the standard model of particle physics, which successfully demonstrates how fundamental particles of matter interact with each other. The problem is that this model does not take into account the existence or gravity of dark matter. WIMPs are heavier than protons and have little interaction with other types of matter, but when two such particles collide, they destroy each other and release energy to other particles, including gamma-ray photons.
To search for gamma rays associated with WIMP collisions, many researchers have focused on dark matter clusters, like the center of the Milky Way. Data collected during 15 years of observations through the Fermi telescope shows that the gamma rays form a halo-like structure similar to what a dark matter halo would have. In addition, these beams are very energetic – another characteristic feature of collisions of putative WIMPs.
But critics of the work note that the signal only appears if the background is eliminated – that is, any source of energetic photons emitted from the Milky Way, including the galaxy's center and disk. A certain amount of energy is also emitted from the Fermi bubbles – two giant regions of gas and cosmic rays hanging over the Milky Way.
Research studying energy sources in the Milky Way must take this background noise into account and “subtract” it to find the true signal. Not to mention that the signal can also depend on the type of dark matter particle – its mass, basic properties and interactions.
However, astronomers from Tokyo are confident that, despite reasonable doubts, their discovery could be outstanding. Not only for the future of astronomical observations but also directly for dark matter modeling.
