According to the calculations of astrophysicists, more than 80% of the Universe is made up of a mysterious matter that does not interact with the electromagnetic field, that is to say that we cannot see it, however, we know that it is there since it is necessary to explain the rotation of galaxies and the conformation of other objects such as clusters of galaxies. The point is that we cannot detect its existence, we only know that it is there because of the clues it gives us and for this reason it has been called dark matter.
What is dark matter and why can’t we see it?
As far as we believe, dark matter makes up 80% of the entire cosmos. Our Universe is made up mainly of material that we do not know, we have never seen and we do not know exactly how it behaves, but we know that it is there, since otherwise the behavior of galaxies, stars and planets would simply not make sense.
Dark matter, therefore, is invisible because it does not emit light or energy that can be captured by our telescopes or their conventional sensors. Why isn’t entirely clear, but researchers believe its elusive nature is due to its composition, which could be very different from visible matter.
Visible matter is called by physicists as baryonic matter, since it is made up of baryons, the general name given to subatomic particles such as protons, neutrons, and electrons. And while there’s a chance that dark matter also contains baryons in its composition, there’s a much bigger chance that it doesn’t. In the latter case, it opens the door for other foreign particles to shape it and give it its slippery and invisible characteristics.
Dark matter candidates
There are many candidates that are emerging as favorites because their characteristics could explain why dark matter is undetectable. The main ones are WIMPS, massive particles with a weak interaction, which stand out for having ten to one hundred times the mass of a proton. However, their weak interactions with baryonic matter make them very difficult to detect.
But they are not the only ones that could be behind the matter. Neutralinos, which are hypothetical massive particles heavier and slower than neutrinos, are also considered candidates for dark matter. But although they exist in theory, their existence has not been proven.
And speaking of neutrinos, there is also a flavor of neutrino that could be emerging as the main component of the mysterious invisible matter. Neutrinos are one of the fundamental particles of the composition of the Universe. They are neutral, incredibly tiny, and rarely interact with other matter. So far it is known that there are three types of neutrinos or ‘flavors’: electron, muon and tau. But there is a fourth flavor that so far only exists in theories called sterile neutrino. Like the other flavors, it wouldn’t have much interaction with other matter and the only way it would do so would be through gravity.
How do we know that dark matter exists?
Until now the existence of dark matter has not been proven, but everything indicates that it does exist, but how do we know this? The answer lies in gravity. For many decades now, astrophysicists have postulated that the estimated amount of matter that exists in the Universe is not consistent with the gravitational interactions within it.
This has been made evident on several occasions, but perhaps the most famous case is that of spiral galaxies. When galaxies of this type were examined in the 1970s, astronomers expected to observe matter in the centers of the galaxies moving faster than that at the outer edges. Instead, they found that the stars at both ends were traveling at the same speed, the only viable explanation being that the galaxies contained more mass than could be observed.
But this example is not the only one that exists. Likewise, if a comparison is made between the amount of mass available in a cluster of galaxies and their gravitational interactions, the clusters simply would not have the ability to stay together. Rather, they would drift apart if only the gravitational fields of visible matter interacted. Once again, the only explanation is the existence of another type of mass that we cannot see but that is there generating gravitational interactions.
in search of evidence
Different telescopes around the world and even in Earth orbit, look every day for clues that help us better understand dark matter. Although we cannot see it, what can be found is the gravitational interactions it generates. There are several projects to detect the way in which dark matter shapes our Universe, one of them is the Dark Energy Survey, which is mainly focused on two foci: the analysis of the distribution of galaxies that directly depends on dark matter and the observation of gravitational lenses. Thanks to these two approaches, they have managed to draw the most complete map of how dark matter is distributed.
The James Webb Space Telescope was recently launched into space, which is equipped with powerful infrared sensors that will help us understand the cosmology of the Universe and with it, the presence and development of dark matter. It seems that this elusive matter is about to be discovered and when it does, it will be a relief for astronomers who have been predicting it for decades.
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