Ordinary matter – basically, anything other than dark matter – makes up about 15% of all matter. But half of it has long been missing. Powerful bursts of radio waves emanating from 69 , The Ghostly Matter That Was Always There. The mystery didn’t lie in whether this matter existed. Cosmological models had predicted its presence for years. But the problem was visibility. The universe’s missing matter didn’t shine, didn’t glow in X-rays or twinkle in ultraviolet., Cosmological models predict that the missing matter can be found in long filaments that extend between matter densities. Astronomers have spotted these filaments, but not with clarity., Another clue about the whereabouts of the missing matter in the Universe has just emerged from amid the largest local cosmic structure. X-ray observations have revealed a massive filament of hot gas, measuring some 23 million light-years in length, in the space between four sub-clusters of galaxies in the enormous, 8,000-galaxy strong Shapley , The astronomers were able to identify and remove any possible 'contaminating' sources of X-rays from the filament using XMM-Newton, leaving behind a pure thread of 'missing' matter., .