Center for Astrophysics An infrared view of NGC6334, the Cat’s Paw Nebula, a giant, star-forming molecular cloud. New submillimeter observations of the southern dark complex in this cloud have uncovered the first prestellar cores (embryos of future stars) ever found in a massive cloud, but they are very cold and cannot be seen in infrared images like this one. ESO/J. Emerson/VISTA Stars form as gravity contracts the gas and dust in an interstellar cloud until cores develop that are dense enough to coalesce into stars. A dense core in the earliest phase of this process is called a starless core, and if it has begun to collapse into a star the stage is referred to as a prestellar core. Prestellar cores can form single or multiple stars under the combined effects of gravity, magnetic fields, and turbulent motions, and understanding these and other properties of prestellar cores is critical to understanding star formation. Prestellar cores in low-mass molecular clouds have been intensively studied, partly because regions of low-mass star formation are relatively close by and comparatively bright. Star formation in massive cluster-forming regions might be quite different – many more massive stars are made there in processes that generally proceed more quickly – but studies of prestellar cores in such regions are very limited. As a result cold, quiescent prestellar cores in massive star-forming regions have not been clearly identified.