Astronomers said Sunday they had for the first time seen the gas strands theorised to hold the universe together in a "cosmic web". They had used the intense radiation generated by a quasar -- a byproduct of a supermassive black hole -- acting as a type of cosmic flashlight to illuminate part of the vast filament network. Cosmologists believe that matter between galaxies is distributed in a network of strands known as the cosmic web. The vast majority of atoms in the universe are thought to reside in this web as hydrogen left over from the Big Bang, and galaxies are believed to form at network nodes. "This is the first time anyone has been able to capture an image of the cosmic web, demonstrating its filamentary structure," said astronomy doctoral student Fabrizio Arrigoni Battaia, who took part in the observations at the Keck Observatory in Hawaii. The team had focused on massive nebula, or deep-space cloud, where the strands intersect. They could study the nebula thanks to illumination provided by a quasar -- radiation generated by cosmic matter falling into a galaxy's central supermassive black hole -- with the aid of computer light filters. Quasars are the most luminous objects in the universe. "In this case, we were lucky that the flashlight is pointing right at the cosmic web, making some of its gas glow," said researcher Sebastiano Cantalupo of the University of California in Santa Cruz. The findings were published in the journal Nature.