Astronomers detected an X-ray signal in a galaxy 240 million light years from us. This signal could be strong evidence for dark matter particles.

The X-ray emission might have been produced by sterile neutrino decay. These sterile neutrinos are one of the proposed particles candidates for dark matter. While more data is necessary to support the claims, researchers believe the X-ray signal, if accurate, could help explain dark matter.

Astronomers predict that 85% of the matter in the universe is dark matter. If the recent claims prove true, it would be a huge step towards understanding the universe.

The X-ray emission lines were found with NASA's Chandra X-ray Observatory and the European Space Agency's XMM-Newton. 73 galaxy clusters were observed; the signal was found in the Perseus galaxy cluster in the form of an emission line, or spike of intensity at a specific level of energy.

Lead author of the Perseus study Esra Bulbul says that a possible explanation for the X-ray emission line is sterile neutrino decay, which is a candidate for dark matter. The lead author of another study using the ESA's XMM-Newton responded to Bulbul's paper, which was released to the public before its peer-review publication, claiming that his team also saw an X-ray emission line in the Perseus galaxy, as well as one in the Andromeda galaxy.

Bulbul's paper is published in the July issue of The Astrophysics Journal.

"We have a lot of work to do before we can claim, with any confidence, that we've found sterile neutrinos. But just the possibility of finding them has us very excited," says co-author Maxim Markevitch of NASA's Goddard Space Flight Center in a press release from the Chandra Observatory.

Uncertainty about the data is due to the limits of the Chandra and the XMM-Newton observatories. Finding the X-ray emission line really pushed the observatories' sensitivity capabilities. There also could be many alternate explanations for the emission line that do not involve sterile neutrinos. In addition, dark matter being composed of sterile neutrinos is still only a theory. If proven, it is also likely that dark matter is made up of other particles and not simply sterile neutrinos.

After Bulbul et al. released the paper to the public, many researchers wrote response papers, some discussing theories in support of the sterile neutrino claim and others expressing their doubts. The research team admits there are many steps to be taken, including launching a new kind of X-ray detector to collect more accurate measurements, but it remains optimistic.

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