Artist's illustration of a quasar similar to APM 08279+5255, where astronomers discovered huge amounts of water vapour. While this figure shows the quasar's torus approximately edge-on, the torus around APM 08279+5255 is likely positioned face-on from our point of view.
Credit: NASA/ESA
PASADENA: The largest and farthest reservoir of water in the known universe has been located. The water, equivalent to 140 trillion times all the water in the world's ocean, surrounds a distant quasar more than 12 billion light-years away.
The quasar is one of the most powerful known objects in the universe and has an energy output of 1,000 trillion suns - about 65,000 times that of the Milky Way galaxy.
The quasar's power comes from matter spiraling into the central supermassive black hole, estimated at some 20 billion times the mass of our Sun, said study leader Matt Bradford of Caltech and NASA's Jet Propulsion Laboratory in California.
"The environment around this quasar is very unique in that it's producing this huge mass of water," said Bradford of the research published in Astrophysical Journal Letters. "It's another demonstration that water is pervasive throughout the universe, even at the very earliest times."
Powered by enormous black hole
A quasar is powered by an enormous black hole that steadily consumes a surrounding disk of gas and dust. As it eats, the quasar spews out huge amounts of energy. Both groups of astronomers studied a particular quasar called APM 08279+5255.
The astronomers expected water vapour to be present even in the early, distant universe, but had not detected it this far away before. There's water vapour in the Milky Way, although the total amount is 4,000 times less than in the quasar, because most of the Milky Way's water is frozen in ice.
Water vapour is an important trace gas that reveals the nature of the quasar. In this particular quasar, the water vapour is distributed around the black hole in a gaseous region spanning hundreds of light-years in size.
Its presence indicates that the quasar is bathing the gas in X-rays and infrared radiation, and that the gas is unusually warm and dense by astronomical standards. Although the gas is at a chilly minus 53 degrees Celsius and is 300 trillion times less dense than Earth's atmosphere, it's still five times hotter and 10 to 100 times denser than what's typical in galaxies like the Milky Way.
May grow six times its size
Measurements of the water vapour and of other molecules, such as carbon monoxide, suggest there is enough gas to feed the black hole until it grows to about six times its size. Whether this will happen is not clear, the astronomers say, since some of the gas may end up condensing into stars or might be ejected from the quasar.
Bradford's team made their observations starting in 2008, using an instrument called 'Z-Spec' at the California Institute of Technology's Submillimeter Observatory, a 10-metre telescope near the summit of Mauna Kea in Hawaii. Follow-up observations were made with the Combined Array for Research in Millimeter-Wave Astronomy (CARMA), an array of radio dishes in the Inyo Mountains of Southern California.
The second group, led by Dariusz Lis, senior research associate in physics at Caltech and deputy director of the Caltech Submillimeter Observatory, used the Plateau de Bure Interferometer in the French Alps to find water. In 2010, Lis's team serendipitously detected water in APM 8279+5255, observing one spectral signature. Bradford's team was able to get more information about the water, including its enormous mass, because they detected several spectral signatures of the water.
