Water, water everywhere... including the early universe
EU-funded astrophysicists have discovered evidence of water vapour in the early universe. The vapour was found in a quasar 11.1 billion light years from Earth; this is the first time water molecules have been detected so far away. The findings, published in the journal Nature, suggest that water may have been more abundant in the early universe than was previously thought. The work was supported in part by the Marie Curie Training Network ANGLES ('Astrophysics network for galaxy lensing studies'), which is financed through the Sixth Framework Programme (FP6). The water was observed in the form of a maser, which is like a laser but at microwave wavelengths. Water masers have been found in a number of nearby galaxies, and they appear to arise in the hot gas and dust that swirl around the super-massive black hole at a galaxy's core. Until now, the most distant galaxy where water had been detected was six billion light years away. This latest discovery only came about thanks to a bit of astronomical trickery: the researchers used a nearby galaxy as a kind of cosmic telescope; the galaxy in the foreground magnified and distorted the light from the distant quasar MG J0414+0534 to form four distinct images of the quasar and strengthened the signal by a factor of 35. 'Others have tried and failed to find water, and we knew we were looking for a very faint signal,' explained Violette Impellizzeri, lead author of the paper and a graduate student at the Max Planck Institute for Radio Astronomy in Germany. 'So we thought of using a foreground galaxy like a cosmic magnifying glass to observe at a far greater distance and [we] had to be persistent, and sure enough the line emission of water popped up.' The newly discovered maser is extremely bright, with a luminosity 10,000 times greater than that of our sun. It is also twice as luminous as the most powerful local water maser. Without the 'gravitational lensing' offered by the galaxy in the foreground, it would have taken 580 days of continuous observations with the Effelsberg 100m radio telescope; as it was, it took just 14 hours to make the discovery. Furthermore, our knowledge of nearby masers suggested that the chances of finding such a bright maser were one in a million. The fact that a maser was found in the first distant galaxy studied suggests that these features may be more common than thought. Crucially, the detection of a water maser 11.1 billion light years away also proves that conditions were right for water molecules to form and survive just 2.5 billion years after the big bang. 'It is interesting that we found water in the first gravitationally magnified object we observed from the distant universe,' commented John McKean, also of the Max Planck Institute for Radio Astronomy. 'This suggests that the water molecule may have been much more abundant in the early universe than first thought, and can be used for further research into super-massive black holes and galaxy evolution.' 'Because water masers arise near the cores of galaxies, our result opens new, interesting possibilities for studying super-massive black holes at a time when galaxies were forming,' added Dr Impellizzeri. 'It will also generate further searches for water in other distant galaxies with the telescopes we have at our disposal today and with the next generation of radio telescopes; we now know water is out there.' Discovering further evidence of water in the far flung reaches of the universe will not be easy until new and more sensitive instruments become available; the researchers expect that the proposed Square Kilometre Array (SKA) telescope, which should be ready for use in around a decade, will lead to new advances in this field.
Countries
Germany, Italy