Finally detected? Elusive dark matter may be streaming from glaring Sun

Finally detected? Elusive dark matter may be streaming from glaring Sun
A European space observatory picked up an unusual signal which British astronomers believe to be the first direct detection of dark matter’s signature. The finding could be a historic breakthrough in our understanding of the universe.

Invisible dark matter – which neither emits or absorbs light – is believed to account for 85 percent of the matter in the universe, and is thought to explain the gravitational pull that keeps galaxies from flying apart.

It has been a mystery for over 30 years – but now a potential clue has been found by scientists in Leicester, UK. An inexplicable signal was discovered in data obtained by nearly 15 years of measurements by the European Space Agency’s orbiting XMM-Newton observatory. A study by astronomers at the University of Leicester will be published on Monday in the Monthly Notices of the Royal Astronomical Society journal.

A sketch (not to scale) showing axions (blue) streaming out from the Sun, converting in the Earth's magnetic field (red) into X-rays (orange), which are then detected by the XMM-Newton observatory. (University of Leicester image)

“The X-ray background – the sky, after the bright X-ray sources are removed – appears to be unchanged whenever you look at it,” explained senior paper author Andy Read in a press release. “However, we have discovered a seasonal signal in this X-ray background, which has no conventional explanation, but is consistent with the discovery of axions.”

Axion is a hypothetical dark matter particle, which has been searched for – unsuccessfully so far – by the European Organization for Nuclear Research (CERN), located in Switzerland. If the Leicester team has indeed detected axion, the particles are incredibly light, with a mass of around a hundred billionth of an electron.

“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.

The researchers noticed a curious background signal component that was greater in summer than in winter. The intensity of x-rays increased by approximately 10 percent whenever the spacecraft observed the boundary of Earth’s magnetic field, facing towards the Sun.

After “all other possible causes of the variability [had been] carefully considered and conclusively ruled out,” the astronomers proposed a new idea which stood out from traditional physics. In fact, Read described it as an “exotic” idea.

Axions are “indeed produced in the core of the Sun and do indeed convert to soft x-rays in the magnetic field of the Earth, giving rise to a significant, seasonally-variable component” of the background radiation, Professor Fraser explained in the paper.

Martin Barstow, president of the Royal Astronomical Society, said: “This is an amazing result. If confirmed, it will be the first direct detection and identification of the elusive dark matter particles and will have a fundamental impact on our theories of the universe.”

The findings may take several years to check, but Read said that a similar signal had been detected by NASA’s Chandra X-ray Observatory. “In a few years, we might be able to double the dataset from XMM-Newton and look at this with more precision,” he said.

The Leicester astronomers shared their excitement over the discoveries that “could be truly ground-breaking, potentially opening a window to new physics, and could have huge implications, not only for our understanding of the true x-ray sky, but also for identifying the dark matter that dominates the mass content of the cosmos.”

The notion of dark matter's existence was first proposed by Swiss astronomer Fritz Zwicky in the 1930s. For decades, scientists studying dark matter were underestimating its vast presence in the universe. It wasn't until 2012 that a new mass-measuring technique revealed that there should be “plenty” of dark matter near the Sun.