An unusual signal picked up by a European space observatory could be the first direct detection of dark matter particles, astronomers say.

The findings are tentative and could take several years to check, but if confirmed they would represent a dramatic advance in scientists’ understanding of the universe.

Dark matter cannot be seen, but the mysterious substance is thought to make up about 85% of all the matter in the universe. The web of dark matter that stretches through space is believed to give the cosmos its structure, although so far it has eluded direct detection by physicists.

Researchers at Leicester University spotted the curious signal in 15 years of measurements taken by the European Space Agency’s orbiting XMM-Newton observatory. They noticed that the intensity of x-rays recorded by the spacecraft rose by about 10% whenever it observed the boundary of Earth’s magnetic field that faces towards the sun.

Andy Read, an astronomer on the team, said that conventional models of the universe failed to explain the effect. Once galaxies, stars and other bright x-ray sources have been filtered out, he said, the intensity of x-rays in space was expected to be the same whenever measurements were taken.

With no explanation in traditional physics, the scientists looked to more outlandish theories. One seemed to fit the bill. It called for theoretical particles of dark matter called axions streaming from the core of the sun and producing x-rays when they slammed into Earth’s magnetic field.

“If the model is right then it could well be axions that we are seeing and they could explain a component of the dark matter that everyone thinks exists,” Read told the Guardian.

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