Dark matter might not be invisible after all. It could leave a hidden glow

Researchers at the University of York propose that light could subtly change color when it encounters dark matter, offering a potential method for detecting it directly. This finding challenges the long-standing belief that dark matter and light do not interact in any measurable way.

Rethinking an "Invisible" Force

Until now, dark matter has been known only through its gravitational influence, which holds galaxies together and shapes their structure. Because it neither emits nor reflects light, scientists have traditionally assumed it cannot be detected through optical means.

The new work, however, suggests this view might be incomplete. According to the York team, light traveling through space could acquire a slight red or blue tint depending on the kind of dark matter it encounters. Detecting these subtle variations could open a new window into studying the unseen material that dominates the cosmos.

A "Six Handshake Rule" for Particles

The research is based on a concept similar to the "six handshake rule." This is the idea that any two people are connected by a short chain of acquaintances. The scientists suggest that something comparable might occur among subatomic particles.

Even if dark matter does not interact directly with light, it could still affect it indirectly through other particles. Certain dark matter candidates, called Weakly Interacting Massive Particles (WIMPs), might influence light by connecting through a chain of intermediate particles such as the Higgs boson and the top quark.

Traces of Color in the Darkness

Dr. Mikhail Bashkanov, from the University of York's School of Physics, Engineering and Technology, explained: "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.

He added: "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."

A New Direction for Dark Matter Detection

The study describes how these indirect interactions could be tested in upcoming experiments, allowing scientists to eliminate certain dark matter models while refining others. The team also emphasizes the importance of incorporating these findings into the design of future telescopes.

Dark matter remains one of physics' greatest mysteries, revealing itself only through its gravitational pull. Confirming these results could provide an entirely new approach to detecting it and deepen our understanding of how the Universe is held together.

Dr. Bashkanov said: "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."

The study was published in the journal Physics Letters B.