This nebula is called the Trifid Nebula, so named for how the dark band of gas separates it into three parts. But this image of the three-lobed nebula reveals another threesome: the three stages of early star formation.
The Trifid Nebula not only appears to have three lobes when observed from afar, but closer inspection reveals that it is actually made of three distinct types of nebula clouds. This image comes from the La Silla Observatory in Chile, and it shows off, in the visible spectrum, the beauty of the Trifid Nebula's three part cosmic factory.
The first part is visible here as the blue section at the top of the image. This is referred to as a reflection nebula. It's basically a giant hazy dust cloud that scatters light shed by newly created stars. The brightest stars born in the Trifid Nebula glow blue, so that mixed with the predominantly blue scattering of this dust cloud creates the blue haze at the top of the Trifid Nebula.
The pink area in the middle of the nebula is due to a pretty typical emission nebula. When the predominant gas in this nebula, hydrogen, is heated by the very new stars in this region, it shines red.
The dark bands that originally earned the nebula its name are actually dark nebulae, or strips of light-obscuring dust. This dust is mostly coalesced from previous star births within the nebula. Eventually, within these darker strips, more gas and dust will pull together, creating new stars.
When taken together, these three component nebulae could be seen as the environs of the very beginning of the star cycle, a sort of factory floor for star creation. It could also be seen as the factory showroom, as these newly created stars interacting with space dust creates a pretty stunning spectacle.
Trisected Nebula Seen in Fresh Detail [LiveScience]