Dark matter is all around us. It doesn't emit or absorb light, but we know it exists and that it makes up over 80 percent of the Universe, holding everything together. But we've never seen dark matter, not even with our most powerful telescopes.
However, now we may have direct proof of dark matter, thanks to a team of scientists at the University of Leicester in England. Using over 15 years of data from the European Space Agency's space observatory, the XMM-Newton, they detected a mysterious signal in the X-ray band of the sky. They believe this signal is coming from axions, which are particles associated with dark matter.
"The X-ray background - the sky, after the bright X-ray sources are removed - appears to be unchanged whenever you look at it," says Dr. Andy Read, from the University of Leicester Department of Physics and Astronomy. "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."
Scientists believe these axions come from the sun's core. As they hit the Earth's magnetic field, they convert to X-rays. In their findings, the team found that these x-ray signals intensified when studying data taken from the side of the Earth's magnetic field that faces the sun.
The first theory of dark matter comes from the 1930s. After astronomer Fritz Zwicky studied the Coma galaxy cluster, he estimated that the cluster held more mass than what we could see. In the 1970s, astronomer Vera Rubin confirmed this by studying individual galaxies, and learning that they, too, had more mass than previously thought.
To account for this extra mass, scientists theorized that an unseen material called dark matter was holding everything together via gravity, basically acting as the glue that bonds everything in the Universe.
Dark matter, though, is elusive because it isn't seen. So finding direct evidence of it could solve a mystery plaguing science for over 30 years.
If the University of Leicester's work receives confirmation from other studies, this could be the one of the most important and ground-breaking discoveries in physics in decades. However, as with all scientific discoveries, confirmation could take several years.
"What's less clear, however, is whether any other explanation of the measured effect can be excluded," says Christian Beck from Queen Mary, University of London. "A true discovery of dark matter that is convincing for most scientists would require consistent results from several different experiments using different detection methods, in addition to what has been observed by the Leicester group."