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"
Symbiotic Star System R Aquarii
04/01/1996
Sometimes stars work together to create a spectacular display. Such is the case with the binary star system R Aquarii - a "symbiotic" star system. Here two stars, a variable giant and a white dwarf companion - create both a nebula and a jet. Light from the giant star and the unusually shaped nebula are visible in the above photograph. The two visible shells in the nebula likely resulted from two separate outburst events. Much about symbiotic star systems remains unknown.