ASTRONOMY: Enhanced: Water's Role in Making Stars.

Water has long been believed to play an important role in star-forming regions as an oxygen reservoir and by cooling the circumstellar gas cloud, but observational evidence has been hard to come by. In her Perspective, Nisini explains how recent satellite missions have provided the first observational evidence that allows chemical models of star formation to be tested. Water is found to be initially low in abundance but to increase in abundance once a protostar has formed. The observations include protostars that are the precursors of sunlike stars, thus shedding light on water production in solar-type systems.