A ball of gas more massive than a billion suns is hurtling like an enormous comet through the interior of a distant galaxy cluster. The massive structure is held together by mysterious dark matter, astronomers said today, but it is steadily breaking apart and becoming fuel for new stars. "This is likely a massive building block being delivered to one of the largest assembly of galaxies we know," said study team member Alexis Finoguenov of the University of Maryland, Baltimore County. The finding is detailed in the June 6 issue of Astrophysical Journal. Great ball of fire The gas blob...