June 25, 2014
Have Astronomers Detected The Particle That Comprises Dark Matter?
redOrbit Staff & Wire Reports - Your Universe Online
Using the ESA’s XMM-Newton and NASA’s Chandra X-ray Observatory, astronomers have located a mysterious X-ray signal that could be produced by sterile neutrinos – particles that are a potential candidate for the abundant and essentially invisible substance known as dark matter.[ What Is Dark Matter?: Podcast Interview With Dr. Matthew Walker ]
Thanks to the two high-powered observatories, Dr. Esra Bulbul of the Harvard-Smithsonian Center for Astrophysics (CfA) and her colleagues discovered a previously undetected X-ray emission line (a spike in intensity at an extremely specific wavelength of X-ray light) during an analysis of 73 galaxy clusters, including the massive Perseus cluster.
“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,” Dr. Bulbul explained in a statement Tuesday. “So we had to look for an explanation beyond the realm of known, ordinary matter.”
Based on their observations, the astronomers believe that these emissions could be produced by the decay of sterile neutrinos, an exotic type of subatomic particle that is believed to exist but has not yet been detected, according to the ESA. Some scientists have suggested that these particles could help partially explain dark matter, the substance said to comprise approximately 85 percent of the universe.
While NASA said the discovery holds “exciting potential,” the space agency also cautions that the findings have to be confirmed with additional data – a necessary step to rule out other possible explanations, and to determine if it is actually plausible that dark matter could have been observed.
“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,” said study co-author Maxim Markevitch, an astrophysicist at the NASA Goddard Space Flight Center in Greenbelt, Maryland.
“We know that the dark matter explanation is a long shot, but the pay-off would be huge if we're right. So we're going to keep testing this interpretation and see where it takes us,” added Dr. Bulbul. A paper detailing the research appears in the June 20 issue of The Astrophysical Journal and posted in the arXiv database.
While the emission line could be the result of sterile neutrinos, there are other possible explanations as well – provided it is even deemed to be real. There are ways that normal matter in the cluster could have produced the line. However, NASA said that the astronomers’ analysis suggests these alternatives would have involved unlikely changes to physical conditions in the galaxy cluster or the atomic physics of extremely hot gases.
Furthermore, even if they are right about the sterile neutrino interpretation, the authors report that the detection does not overtly imply that all of dark matter is composed of these particles. They now plan to combine data from Chandra and JAXA’s Suzaku mission to see if they can find the same X-ray signal in a larger number of galaxy clusters.