A new study conducted by scientists from the University of Michigan and University of California has revealed that dark matter is not behind mysterious electromagnetic (X-ray) signals detected from galaxies and galaxy clusters.
In 2014, another group of researchers spotted an unidentified X-ray emission line around 3.5 kilo-electron volts (keV). At the time, scientists thought this energy was being produced by decaying dark matter, which scientists assumed might be comprised of a hypothetical subatomic particle called a sterile neutrino.
Sterile neutrinos are believed to be very unstable. They decay into ordinary neutrinos releasing electromagnetic radiation. To produce an X-ray line of 3.5 keV, sterile neutrinos would have had to have a mass around 7 keV.
Scientists from the University of Michigan and University of California later decided to put this hypothesis to the test. If true, the same emission line should be present in our galaxy. Using the XMM-Newton (X-ray Multi-Mirror Mission) space telescope, they analysed blank-sky regions of the Milky Way, but found no evidence for the emission line.
The new study, however, does not disprove the hypothesis that dark matter consists of sterile neutrinos. It means that sterile neutrinos might have a different mass so they produce an X-ray emission of another energy.
"Our finding does not mean that the dark matter is not a sterile neutrino, but it means that - contrary to what was claimed in 2014 - there is no experimental evidence to-date that points towards its existence”, said Ben Safdi, co-author and an assistant professor of physics at the University of Michigan.
As sad as it may seem, scientists say this setback will actually help them in further attempts to detect dark matter. "While this work does, unfortunately, throw cold water on what looked like what might have been the first evidence for the microscopic nature of dark matter, it does open up a whole new approach to looking for dark matter which could lead to a discovery in the near future", Safdi concluded.
In other scientific news, a group of international scientists has suggested the answer to the mystery of dark matter could be right under our feet.