Article: This Mysterious Signal 'Could Not Be Explained By Known Physics,' Astronomers Say
"Signal" is a misleading word. It implies an intelligent source. It is not.
When excited atoms release energy, they release the energy as specific wavelengths of electromagnetic radiation. Sodium vapor or mercury vapor lights in parking lots are an example. Sodium vapor lights only release energy in the yellow part of the visible light.
Researchers were observing the electromagnetic spectrum from the Perseus Cluster. It "is surrounded by a cloud of superheated gas, which contains ions that each emit their own 'line' in the x-ray spectrum."
They found lines in the spectrum that could not be accounted for by any known ions.
They speculate that they may have found evidence for so-called "dark matter."
Dark matter is called that because we cannot detect it other than by the effects of its mass on galaxies and clusters of galaxies. It has to be there to provide the gravitational attraction that holds galaxies together. It is otherwise invisible.
Or it may be due to something else entirely.