Researchers at the University of York discovered that dark matter could create subtle, quantifiable effects on light as it travels through areas containing this elusive substance, thereby questioning longstanding beliefs that the two do not interact. The study was published in the journal Physics Letters B.
Studies indicate that light could pick up a subtle tint of red or blue, depending on the type of dark matter. Image Credit: University of York
Dark matter, the material constituting the majority of the Universe, may be detectable as a red or blue light ‘fingerprint,’ according to new research.
The existence of dark matter is inferred entirely from its gravitational effects, the invisible force that shapes galaxies and holds them together. Because it doesn’t emit, absorb, or reflect light, few believe it could ever be directly observed through electromagnetic means.
Subtle Tint
However, the York team suggests that the situation may be more intricate. Their research implies that light could acquire a subtle hue, either slightly red or blue, based on the type of dark matter it encounters. The ability to detect such phenomena could pave the way for a novel approach to examining the unseen mass that governs the Universe.
The theoretical analysis employs the concept of the "six handshake rule", the idea that any two individuals on Earth are linked through only a few mutual acquaintances. They propose that a comparable network of connections may exist among particles.
Even if Dark Matter does not interact directly with light, it may still exert an indirect influence through other particles. For instance, certain Dark Matter candidates, referred to as Weakly Interacting Massive Particles (or WIMPs) could connect to light through a sequence of intermediary particles such as the Higgs boson and the top quark.
Next Generation
It’s a fairly unusual question to ask in the scientific world, because most researchers would agree that Dark Matter is dark, but we have shown that even Dark Matter that is the darkest kind imaginable - it could still have a kind of color signature.
Dr. Mikhail Bashkanov, School of Physics, Engineering and Technology, University of York
“It’s a fascinating idea, and what is even more exciting is that, under certain conditions, this ‘color’ might actually be detectable. With the right kind of next-generation telescopes, we could measure it. That means astronomy could tell us something completely new about the nature of Dark Matter, making the search for it much simpler,” said Bashkanov.
The research outlines methods for investigating these indirect particle interactions in upcoming experiments and approaches that could help scientists rule out certain dark matter theories while narrowing in on others. As a result, the researchers argue that this study underscores the importance of factoring in such interactions when designing the next generation of telescopes.
Searching the Skies
Comprehending dark matter continues to be one of the most significant challenges in contemporary physics, and thus, the subsequent phase of this research may involve validating these discoveries, which could provide a novel approach to seeking a substance that has, up to this point, only manifested itself through gravitational effects.
Right now, scientists are spending billions building different experiments - some to find WIMPs, others to look for axions or dark photons. Our results show we can narrow down where and how we should look in the sky, potentially saving time and helping to focus those efforts.
Dr. Mikhail Bashkanov, School of Physics, Engineering and Technology, University of York
Journal Reference:
Acar, A., et al. (2025) Dark matter: Red or blue? Physics Letters B. doi.org/10.1016/j.physletb.2025.139920