Hot Water
Thursday, October 30, 2008
Science Update - A look at CfA discoveries from recent journals

In 1998, a NASA team led by SAO astronomers launched a space mission to study water in space (and some other key molecules and atoms as well). The satellite, the Submillimeter Wave Astronomy Satellite (SWAS), successfully completed its primary mission in 2005. SWAS found water nearly everywhere it looked, and its data prompted SAO scientists to conclude that at least this requirement for life was present throughout the cosmos. But there was one outstanding puzzle lurking in SWAS's discovery of water: there was less of it (in relation to other molecules) than had been expected.

Since water is critical to life, astronomers want to understand not only where it is, but how much exists, and why. One solution to the puzzle subsequently proposed by the team was that considerable amounts of water are frozen out onto the surfaces of cold grains of dust where the molecules could not be detected by SWAS.

SAO astronomers from the SWAS team, Gary Melnick and Volker Tolls, along with six colleagues, have recently obtained new results from the Spitzer Space Telescope that suggest another option for water: it is very hot. Their data are the first detections of extended, hot water vapor with high spatial resolution imaging. SWAS, although it too had concluded there was hot water present, did not have the spatial resolution needed to quantify that conclusion. The astronomers looked at a region of young star formation with fast-moving, bi-polar jets of ejected material. Those jets produce shocks that have two effects on water -- they can evaporate the ice from surfaces of dust grains, and they can heat the water to temperatures as high as 1500 degrees kelvin. The new results show that, at least in some regions, the total amount of water agrees with that predicted by chemical models to within the uncertainties, and lend confidence to our general understanding of this vital constituent of the cosmos.