All our observations indicate that dark matter and light are united only by gravity. For example, when dark matter clusters around a galaxy, its gravitational pull can deflect light. This allows us to map the distribution of dark matter in the universe by observing how light is gravitationally lensed around it.

We also know that dark matter and ordinary matter interact gravitationally. The gravity of dark matter causes galaxies to gather into superclusters.

But the question of whether dark and simple matter interact only gravitationally remains unanswered. If an atom and a dark matter particle intersect, do they just pass through each other?

Since we have not observed dark matter particles directly, we can only speculate, but most dark matter models claim that gravity is the only common link between light and ordinary matter. Dark and simple matter condense around each other, but collide and merge like interstellar clouds.

However, a new study shows that they interact, which could reveal subtle aspects of the mysterious matter. The study examines six superdim dwarf galaxies, SKGs. These are satellite galaxies of the Milky Way that appear to have far fewer stars than their mass would suggest.

This is because they consist mainly of dark matter. If ordinary and dark matter interact only gravitationally, then the distribution of stars in these small galaxies should follow a certain pattern. If dark and simple matter interact directly, this distribution will be skewed.

To test this, the team conducted computer simulations of both scenarios. They found that in the non-interacting model, the distribution of stars should be denser in the center of the SCG and more diffuse on both sides.

In a model that takes into account the interaction, the distribution of stars should be more uniform. By comparing these models with observations of six galaxies, the scientists found that the interacting model described reality slightly better.

It appears that dark matter and ordinary matter interact not only through gravitational attraction. We do not yet have enough data to determine precisely the nature of the interaction, but the very fact that there is an interaction is surprising.

This means that our traditional models of dark matter are at least partially wrong. This may point the way to new methods for direct detection of dark matter.