nebula
noun /ˈnebjələ/
  /ˈnebjələ/
 (plural nebulae 
 (astronomy) /ˈnebjəliː/
  /ˈnebjəliː/
)- a mass of dust or gas that can be seen in the night sky, often appearing very bright; a bright area in the night sky caused by a large cloud of stars that are far awayTopics Spacec2Word Originmid 17th cent. (as a medical term): from Latin, literally ‘mist’.