Watery disks

Abstract

The paradigm for star formation is understood to center around the formation of a rotating disk from a cloud of gas and dust. The circumstellar disk funnels material onto the newly formed central star and also serves as a reservoir of material from which a planetary system may arise. Determining the physical and chemical composition of these disks is necessary to understand the formation and evolution of planets. Previous observations have detected the presence of molecules within the disk, thereby demonstrating an active chemical network. However, this chemistry is harder to trace in the majority of the disk where low temperatures result in the molecules freezing out onto grains. On page 338 of this issue, Hogerheijde et al. (1) use the Herschel Space Observatory to detect cold water vapor in one of the closest young stars, TW Hydrae. The source of that water vapor is likely to be a large reservoir of ice grains.