Found: 7 percent of the mass of the universe. Missing since: 10 billion years ago. Consider one more astronomical mystery solved. Scientists have located a sizeable chunk of the universe that seemed to be missing since back when the stars first formed. It’s floating in super-hot rivers of gas, invisible to the naked eye, surrounding galaxies like our own. And a completely different kind of mystery matter -- dark matter -- may have put it there. The results appear in the current issue of the journal Nature. To make this latest discovery, astronomers at Ohio State University and their colleagues...
