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"
Zooming in to the Pelican Nebula
02/07/2007
Where is the Pelican Nebula? APOD features many objects in the night sky, but usually does not have the resources to show where each one lies. Today, thanks to inventive digital manipulations of Filipe Alves, it is possible to show you exactly where the photogenic Pelican Nebula can be found. Clicking on the arrow will cause many browsers to download and play a spectacular movie that zooms from the perspective of an unaided human eye to that of a powerful telescope. The observatory dome visible on the right is part of Calar Alto Observatory in southern Spain. The image zooms into the constellation of Cygnus, passes the greater Pelican Nebula (IC 5070), and settles on a dust structure in the Pelican head housing unborn stars. Alternatively, the movie is also available here.