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"
NGC 2392 from Hubble
07/04/2002
In 1787, astronomer William Herschel discovered NGC 2392. From the ground, NGC 2392 resembles a person's head surrounded by a parka hood. In 2000, the Hubble Space Telescope imaged NGC 2392. From space, the nebula displays gas clouds so complex they are not fully understood. NGC 2392 is clearly a planetary nebula, and the gas seen above composed the outer layers of a Sun-like star only 10,000 years ago. The inner filaments visible above are being ejected by strong wind of particles from the central star. The outer disk contains unusual light-year long orange filaments. NGC 2392 lies about 5000 light-years away and is visible with a small telescope in the constellation of Gemini.