What is dark matter? Dark matter is a mysterious substance that many physicists believe makes up a large proportion of the total mass of the universe, despite never having directly observed it. It is invisible to light and other forms of electromagnetic radiation, so modern instruments cannot “see” it . But it has mass, and that means it has a gravitational pull. So we infer that dark matter permeates our entire universe; in fact, it makes up about 84% of the mass of the cosmos.
According to the prevailing theory, because dark matter does not emit any type of electromagnetic radiation, its particles do not interact with those of baryonic matter or ordinary matter, except through gravity. However, a new study carried out by scientists from the International School for Advanced Studies (SISSA) in Italy has found, for the first time, evidence of a direct interaction between the two types of matter.
The researchers expose, in their work published in the journal Astronomy & Astrophysics, that the huge region of dark matter particles that surrounds the universe has two main characteristics: a density that is constant up to a certain radius that expands amazingly over time, while that the density decreases. What implications does this result have? That there is a direct interaction between the particles that make up the dark matter halo and those that make up the ordinary matter that we are all made of: galaxies, planets, and you and me. Four times more abundant than the matter that forms stars and galaxies, dark matter is the backbone of the cosmos.
Dark matter, that elusive element of the universe
This new approach collides head-on with the theory that describes the universe, which postulates that cold dark matter particles are inert and do not interact with any other particles, except gravitationally.
The authors surveyed a host of distant galaxies some 7 billion light-years away from us, getting a new look at one of the biggest mysteries in modern physics : elusive dark matter.
“Its dominant presence in all galaxies arises from the fact that stars and hydrogen gas move as if governed by an invisible element,” explains Gauri Sharma, leader of the work. Unlike previous research, explains Sharma, “in this study, for the first time, we sought to observe and determine the mass distribution of spiral galaxies with the same morphology as the nearby ones, but much further away and therefore earlier. in about seven billion years. The idea is essentially that these progenitors of spiral galaxies like our own could offer fundamental clues about the nature of the particle at the heart of the dark matter mystery.”
They investigated the movement of stars in approximately 300 distant galaxies and “we discovered that these objects also had a halo of dark matter and that, starting from the center of a galaxy, this halo effectively has a region in which its density is constant”, says Paolo Salucci co-author of the study.
It is a feature previously observed in nearby galaxies, experts clarify.
So if there is a region with a constant density of dark matter, among other things, it could only be explained by an interaction between the two particles. In this way, “in our research we offer evidence of interaction between dark matter and ordinary matter that, over time, slowly builds a region of constant density from the center of the galaxy to the outside.”
What is perhaps even more striking is that this region of constant density continues to expand over time.
“Over time , the interaction effect we propose means that these particles were either captured by stars, or else ejected to the outer reaches of the galaxy . This process creates a spherical region of constant density within the dark matter halo, with dimensions that increase proportionally with time and eventually reach those of the galactic stellar disk, as we describe in the article,” say the scientists.
Referencia: G. Sharma et al, Observational evidence of evolving dark matter profiles since z 1, Astronomy & Astrophysics (2022). DOI: 10.1051/0004-6361/202141822