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"
Monsters of IC 1396
25/04/2011
Is there a monster in IC 1396? Known to some as the Elephant's Trunk Nebula, parts of the glowing gas and dust clouds of this star formation region may appear to take on foreboding forms, some nearly human. The entire nebula might even look like a face of a monster. The only real monster here, however, is a bright young star too far from Earth to be dangerous. Energetic light from this star is eating away the dust of the dark cometary globule at the top right of the image. Jets and winds of particles emitted from this star are also pushing away ambient gas and dust. Nearly 3,000 light-years distant, the IC 1396 complex is relatively faint and covers a region on the sky with an apparent width of more than 10 full moons. Recently, over 100 young stars have been discovered forming in the nebula.