X-Rays May Reveal New Clues about Mysterious Dark Matter in Galaxy Clusters

Astronomers have uncovered a new clue when it comes to understanding mysterious dark matter. They've used ESA and NASA high-energy observatories in order to learn a bit more about the elusive ingredient of our universe.

Dark matter neither emits nor absorbs light, but is thought to make up approximately 85 percent of our universe. It can actually be detected through the gravitational influence on the movements and appearance of other objects in the universe, such as stars or galaxies. However, this is mostly indirect evidence, which makes studying dark matter difficult. Yet scientists may have found uncovered new clues when it comes to this particular type of matter.

In this case, the scientists turned to galaxy clusters. These large cosmic assemblies of matter are bound together by gravity. Containing hundreds of galaxies and a huge amount of hot gas filling the space between them, galaxy clusters may just be the perfect way to take a closer look of gravitational influence and, in turn, measure dark matter.

The gas that makes up these galaxies is mainly hot hydrogen at temperatures of over 10 million degrees Celsius. This hydrogen is actually hot enough to emit X-rays. In addition, traces of other elements contribute to addition X-ray "lines" at specific wavelengths. In order to learn a bit more about dark matter, the researchers measured the characteristic lines in 73 galaxy clusters and found an intriguing faint line at a wavelength never seen before.

"If this strange signal had been caused by a known element present in the gas, it should have left other signals in the X-ray light at other well-known wavelengths, but none of these were recorded," said Esra Bulbul, one of the researchers, in a news release. "So we had to look for an explanation beyond the realm of known, ordinary matter."

In this case, researchers believe the emission may be created by the decay of an exotic type of subatomic particle known as a "sterile neutrino," which is predicted but not yet detected.

"If the interpretation of our new observations is correct, at least part of the dark matter in galaxy clusters could consist of sterile neutrinos," said Bulbul.

The findings reveal possible new clues about the nature of dark matter in our universe. This new emission and the X-rays that were detected could pave the way when it comes to finding the first direct sign of dark matter.

The findings are published in The Astrophysical Journal.