Nebula
A nebula is a giant cloud of gas (mostly hydrogen and helium) and cosmic dust situated between stars in the interstellar medium. Nebulae serve as sites of stellar birth and death—including emission nebulae that glow from ionized gas, reflection nebulae that scatter starlight, and dark nebulae that obscure background stars.
Source: science.nasa.gov
APODs including "Nebula"
The Annotated Galactic Center
11/11/1997
The sky toward the center of our Galaxy is filled with a wide variety of celestial wonders. Most are visible with only binoculars. Constellations of nearby stars include Sagittarius, Libra, Scorpius, Scutum, and Ophiuchus. Nebulae include Messier Objects M8, M16, M17, M20 and the Pipe Nebula. Open clusters include M6, M7, M18, M21, M23, M24, M25. Globular clusters include M9, M22, M28, M54, M69, M70. And don't forget Baade's Window. Click on the photo to get the un-annotated version.