The youngest protostellar objects show many signs of rapid development from their initial, spheroidal configurations. Watson et al. find in NGC1333 — IRAS4B a rich emission spectrum of H2O, at wavelengths 20–37 mm, which indicates an origin in extremely dense, warm gas. They model the emission as infall from a protostellar envelope onto the surface of a deeply embedded, dense disc. This is the only example in a sample of 30 class 0 objects, perhaps arising from a favourable orientation or this may be an early and short-lived stage in the evolution of a protoplanetary disk.
- Dan M. Watson
- C. J. Bohac
- J. R. Houck
