A water cloud containing the equivalent of 140 trillion times the water held in Earth's oceans has been detected around a quasar powered by a giant black hole 12 billion light years away.

Although water is expected even earlier in the Universe's existence, the discovery pushes the detection of water one billion years closer to the start of the Universe than any previous find. “It’s another demonstration that water is pervasive throughout the Universe, even at the very earliest times,” says Matt Bradford, lead author of the paper describing the results that will appear in Astrophysical Journal Letters.

The quasar, APM 08279+5255, is powered by a black hole 20 billion times more massive than our Sun and was scrutinized by the Z-Spec instrument at the ten-metre Caltech Submillimeter Observatory in Hawaii, which revealed the spectral fingerprint of water. Confirmation came from the Combined Array for Research in Millimeter-Wave Astronomy (CARMA), a linked array of 15 radio telescope dishes in California.

The water-rich cloud spans hundreds of light years around the black hole, boasting 4,000 times more water vapor than our own Milky Way – most of our Galaxy's water is frozen. The most surprising aspect of the discovery was that the vapor is five times hotter and 10-100 times denser than that observed in galaxies like the Milky Way. X-ray and infrared radiation pour out from the quasar, and may provide the explanation.

“We know that water molecules are formed in regions that are hot and dense,” explains co-author Alberto Bolatto of the University of Maryland. “In a colder environment a lot of the water vapor would stick to interstellar dust grains, coating them with a film of ice. Here, that is not possible because the dust grains themselves are hot, and in fact any ice-coated grain brought to the vicinity of the quasar would have its mantle evaporated, so that may help explain the unusual abundance of water around APM 08279 too. Finally, exciting water vapor molecules to the point that they emit in the lines we observe also requires a high radiation field (or a high temperature and density), so the radiation field not only helps the chemistry that makes water, but it also helps in making it emit at the wavelengths we observe.”

As to the fate of the vapor cloud, some material may clump and condense into stars or alternatively be ejected by the quasar, while some might fall into and feed the black hole – estimates based on the quantity of material observed suggest that it could grow up to six times its present size.