Physicists at the University of Copenhagen believe they may be closing in on one of the biggest mysteries in modern science: the identity of dark matter.
This invisible substance makes up most of the Universe’s mass, yet has never been directly detected. Now, by studying the radiation from distant supermassive black holes as it passes through the immense magnetic fields of galaxy clusters, the researchers have spotted tantalising signs of the elusive axion particle.
If confirmed, the axion could finally reveal what dark matter is made of and transform our understanding of how the Universe holds itself together.
Why the axion particle matters
The axion particle was first proposed in the late 1970s as a solution to a puzzle in quantum physics. Over time, scientists realised axions could also be the missing ingredient in dark matter.
Dark matter is the unseen glue that binds galaxies together. It neither emits nor absorbs light, but its gravitational pull shapes the structure of the cosmos.
Scientists estimate it makes up about 80% of all matter, yet no one has ever directly observed it. Detecting axions would therefore represent a seismic breakthrough in both particle physics and cosmology.
Galaxy clusters: Extreme laboratories in space
Galaxy clusters are the heaviest known structures in the Universe, weighing more than a quadrillion times the mass of the Sun. They host vast magnetic fields capable of influencing light on its billion-year journey across space.
The Copenhagen researchers focused on radiation streaming out from 32 supermassive black holes situated behind galaxy clusters.
These black holes are among the brightest beacons in the Universe, producing intense radiation as they consume surrounding matter.
When this radiation passes through the clusters’ magnetic fields, theory suggests it could briefly convert into axions.
Detecting such a conversion is extremely challenging because the signal is vanishingly faint – easily lost in the background noise of the Universe.
A clever way to hear a “cosmic whisper”
Individually, each black hole offered no clear evidence. But by pooling data from all 32 sources, the researchers created a composite picture.
What once looked like random noise began to form a recognisable step-like pattern, closely matching the predicted fingerprint of axion particles.
This is not yet proof, but it is a powerful hint. The results suggest that the axion particle may finally be within reach of discovery. More importantly, the method can be repeated and refined by research teams worldwide.
Narrowing the hunt for dark matter
The study also helped eliminate entire ranges of energy where axions cannot exist, effectively shrinking the search space. By combining astrophysical observations in this way, physicists can gradually box in the axion particle until its hiding place is revealed.
The Copenhagen team’s approach is not limited to gamma rays. It could also be applied to X-rays or other wavelengths, multiplying opportunities to detect the elusive particle.
This flexibility opens a promising new frontier in particle physics – one that extends far beyond the capabilities of Earth’s most advanced accelerators.
Toward solving the Universe’s greatest mystery
The existence of dark matter has been one of the greatest puzzles in science for nearly a century. Without it, our current models of the Universe simply do not hold together.
If the axion particle is confirmed, it would solve two fundamental mysteries at once: a longstanding gap in particle physics theory and the true nature of dark matter.
Such a discovery would not only explain the invisible structure of the cosmos but also reshape our understanding of its origin and destiny.
For now, the findings remain an exciting hint rather than a conclusive detection. But by looking outward instead of inward, using galaxy clusters as cosmic laboratories, physicists at the University of Copenhagen have opened a powerful new path forward.
