An illustration of the cosmic web where the universe's missing matter was discovered (Image credit: ESA/XMM-Newton and ISAS/JAXA.) Astronomers have discovered a vast tendril of hot gas linking four galaxy clusters and stretching out for 23 million light-years, 230 times the length of our galaxy. With 10 times the mass of the Milky Way, this filamentary structure accounts for much of the universe's "missing matter," the search for which has baffled scientists for decades.This "missing matter" doe...