Mysterious X-ray Signal Hints At Dark Matter

Astronomers using the Chandra X-ray Observatory and the XMM-Newton have recorded an unusual emission of X-ray light from a remote cluster of galaxies which may turn out to be evidence of dark matter. Astronomers think dark matter constitutes 85% of the matter in the Universe, but does not emit or absorb light like “normal” matter such as protons, neutrons and electrons that make up the familiar elements observed in planets, stars, and galaxies. Because of this, scientists must use indirect methods to search for clues about dark matter. he latest results from Chandra and XMM-Newton consist of an unidentified X-ray emission line, that is, a spike of intensity at a very specific wavelength of X-ray light. Astronomers detected this emission line in the Perseus galaxy cluster using both Chandra and XMM-Newton. They also found the line in a combined study of 73 other galaxy clusters with XMM-Newton. ... The authors suggest this emission line could be a signature from the decay of a "sterile neutrino." (Abstract.) Sterile neutrinos are a hypothetical type of neutrino that is predicted to interact with normal matter only via gravity. Some scientists have proposed that sterile neutrinos may at least partially explain dark matter.

Re:Doesn't jive for me

[Anonymous Coward]

Defining dark matter as having zero interaction with electromagnetism is at best a terse over-simplification and at worst just wrong. Dark matter does not strongly interact with electromagnetism, meaning that it for the most part doesn't interfere with light other than from gravity in places we think there are lots of it. But that doesn't preclude it from having rare or much harder to see interactions, such as decays, or rare interactions with high energy photons, or creating Cerenkov radiation when passing through a detector as some experiments are looking for. For a while, astronomers wondered if dark matter could literally just be chunks of rock or black holes, otherwise normal matter that absorbed but didn't emit light. Although surveys of the sky set upper bounds on the amount of such things to be too low. Further evidence suggests it isn't made out of normal things like protons. But none of that means it can't have weak or rare interactions with light, just that whatever interaction there is has to be weak enough to not have conflicted with previous observations.