M16 is a vast star cluster inside an enormous emission nebula. The young stars in the cluster include many O- and B-type giants, which interact with gas in the nebula and cause it to glow.
M16 is also known as the Eagle Nebula, and it is easy to see why: the dark area near the center of this image, an opaque cloud of dust and gas, really does resemble an enormous bird of prey. The eagle is sharply delineated because the gas that composes it carries a different electrical charge from the red gas surrounding it. The same phenomenon occurs in the dark horizontal band in the upper left corner.
New stars are forming inside the nebula, although most are hidden by dark material and so
