"We Truly Don't Know What It Is" --Mystery Milky-Way Spectrum of Light Observed 'Not Produced By Any Known Emission' April 17, 2018 "We use special telescopes to catch X-ray light in the sky, and while looking at these X-rays, the telescopes noticed an unexpected feature and captured a spectrum of light, which is not produced by any known atomic emission," said University of Miami astrophysicist Nico Cappelluti. "This emission line is now called the 3.5 kiloelectron volt (keV). One interpretation of this emission line is that it's produced by the decay of dark matter." "This 3.5 keV emission line is...