The W51 cloud complex is one of the best laboratories in our Galaxy to study high-mass star formation. At a distance of about 5 kpc, it is the closest region containing a high-mass protocluster, and it has two. The cloud includes a long infrared-dark cloud, is interacting with a supernova remnant, and contains a variety of unique massive protostellar sources. This article is an observational review of the region.
Categories: astro-ph.GA