Discovery of Interstellar Heavy Water

Abstract

We report the discovery of doubly deuterated water (D 2 O, heavy water) in the interstellar medium. Using the James Clerk Maxwell Telescope and the Caltech Submillimeter Observatory 10 m telescope, we detected the 1 10-1 01 transition of para-D 2 O at 316.7998 GHz in both absorption and emission toward the protostellar binary system IRAS 162932422. Assuming that the D 2 O exists primarily in the warm regions where water ices have been evaporated (i.e., in a "hot corino" environment), we determine a total column density of N(D 2 O) of cm 2 and a fractional abundance of. The derived column density ratios for 13 10