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"
Night Hides the World
07/02/2014
Stars come out as evening twilight fades in this serene skyscape following the Persian proverb "Night hides the world, but reveals a universe." In the scene from last November, the Sun is setting over northern Kenya and the night will soon hide the shores of Lake Turkana, home to many Nile crocodiles. That region is also known as the cradle of humankind for its abundance of hominid fossils. A brilliant Venus, then the world's evening star, dominates the starry night above. But also revealed are faint stars, cosmic dust clouds, and glowing nebulae along the graceful arc of our own Milky Way galaxy.