Dark Clouds on the Milky Way's Horizon
Astronomers have found cosmic clumps so dark, dense and dusty that they throw the deepest shadows ever recorded. The clumps 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.
The large cloud looms in the very center of this image of the galactic plane from Spitzer. A new study takes advantage of the shadows cast by the cloud's darkest clumps to measure the cloud's overall structure and mass. 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. The background image combines data from the Spitzer GLIMPSE and MIPSGAL surveys. Blue represents 3.6-micron light and green shows light of 8 microns, both captured by Spitzer's infrared array camera. Red is 24-micron light detected by Spitzer's multiband imaging photometer.