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"
M78 and Orion Dust Reflections
24/01/2017
In the vast Orion Molecular Cloud complex, several bright blue nebulas are particularly apparent. Pictured here are two of the most prominent reflection nebulas - dust clouds lit by the reflecting light of bright embedded stars. The more famous nebula is M78, in the image center, cataloged over 200 years ago. To its left is the lesser known NGC 2071. Astronomers continue to study these reflection nebulas to better understand how interior stars form. The Orion complex lies about 1500 light-years distant, contains the Orion and Horsehead nebulas, and covers much of the constellation of Orion. Almost Hyperspace: Random APOD Generator