The photogenic M16 shown above is composed of a young star cluster associated with a spectacular emission nebulae lined with clouds of interstellar dust. The gorgeous spectacle lies toward the galactic center region, some 7,000 light years distant in the constellation Serpens. Most of the stars in the cluster can be seen offset just above and to the right of the photograph's center. This type of star cluster is called an "open" or "galactic" cluster and typically has a few hundred young bright members. The redness of the surrounding emission nebula gas is caused by electrons recombining with hydrogen nuclei, while the dark regions are dust lanes that absorb light from background sources. The dust absorbs so much light it allows astronomers to determine which stars are inside the nebula and which are in the foreground. Stars are forming within the nebula, also known as the Eagle Nebula.