A knot of massive young stars called the Trapezium Cluster shines brightly in this infrared image of the large molecular hydrogen cloud surrounding the Great Nebula in Orion, roughly 1,350 light years from Earth. These stars, numbering about a dozen, are much brighter and more massive than the other young stars in this region, a chaotic star forming nursery. Not only do they flood the central region with light that obscures their individual identities, but they illuminate the rest of the gossamer cloud, about 99 percent of which is molecular hydrogen with trace elements of carbon monoxide and ammonia. Dust particles in the cloud are the main feature responsible for scattering the starlight. The portion of the cloud seen in this photo extends about 30 light years from top to bottom, or eight times the distance between our solar system and the nearest star. It represents a small point in a region just below the famous three-star belt in the constellation Orion. In this plot of the larger region studied, the belt would be just off the image above top of the plot, while the bright star Rigel, marking Orion's left knee, would be just off the bottom of the plot to the right. A zoomable image can be found here. And more information on the Joint Astronomy Centre that put together the image can be found here. The light from the stars in and around the cloud is most effectively scattered at 3.6 microns, which accounts for the picture's eerie green hue.
Photo: UKIRT/JAC, Spitzer Telescope