Astronomers have found cosmic clumps so dark, dense and dusty that they throw the deepest shadows ever recorded. The clumps, shown here in a zoom-in detail, were discovered within a huge cosmic cloud of gas and dust. Infrared observations from NASA's Spitzer Space Telescope of these blackest-of-black regions in the cloud paradoxically light the way to understanding how the brightest stars form.

A new study takes advantage of the shadows cast by these dark clumps to measure the cloud's overall structure and mass. These dense, clumpy pockets of star-forming material within the cloud are so thick with dust that they scatter and block not only visible light, but almost all background infrared light as well.

The dusty cloud, the results suggest, will likely evolve into one of the most massive young clusters of stars in our galaxy. The densest clumps will blossom into the cluster's biggest, most powerful stars, called O-type stars, the formation of which has long puzzled scientists. These hulking stars have major impacts on their local stellar environments while also helping to create the heavy elements needed for life.

This image reveals the overall darkness of the cloud, calculated using Spitzer's infrared observations at a wavelength of 8 microns. Artifacts left by individual stars have been removed from the data, though several large, particularly bright areas have left white artifacts in the cloud map.