nebula
noun
definition 1: a cloud of interstellar dust or gas or both, that may appear as either a light or dark mass depending on how it absorbs, reflects, or re-emits incident radiation.
definition 2: a similar luminous mass of stars too far away to be seen as individual bodies; galactic nebula.
example: The famous Crab Nebula was formed by a supernova explosion that was observed from Earth in 1054.
Word History
Nebula is a Latin word that means “cloud or mist.” It entered the English language in the 1500s as a term for the clouding of the eye we now call a “cataract.” In the 1700s, “nebula” became a term in astronomy.