Planet-Forming Disk Soaked In Cold Water

Astronomers operating the European Space Agency’s Herschel Space Observatory have discovered large amounts of cold water vapor—likely emanating from icy grains—in a planet-forming disk surrounding the newly forming star TW Hydrae (Science, DOI: 10.1126/science.1208931). Until now, astronomers had only been able to detect hot water vapor from the fiery, inner regions of protosolar systems. Michiel R. Hogerheijde of Leiden University and colleagues used the observatory’s Heterodyne Instrument for the Far-Infrared to characterize the type and amount of water and pinpoint its location near the outer region of the disk. This detection of cold water vapor “demonstrates the presence of a considerable reservoir of water ice in this protoplanetary disk, sufficient to form several thousand Earth oceans’ worth of icy bodies,” the researchers write. The region of the disk where the icy water was detected is the same region in our solar system populated by icy comets.