The term was originally used for any extended astronomical object, and was used to describe the Andromeda Galaxy at one time.
Barnard 33 is an example of a dark one. The Wings of the Butterfly one and the Red Square one are examples of the bipolar type. The Pleiades is an example of a reflection type, which do not produce much visible light, and the Omega one is an example of an emission type, which contain ionized gas. Italo Calvino wrote in his short story At Daybreak about living in one. The term was originally used for any extended astronomical object, and was used to describe the Andromeda Galaxy at one time. (*) The Eagle one contains the Pillars of Creation, and other notable ones include the Cat's Eye and Crab ones. FTP, give the name for an interstellar cloud of dust, gas, and plasma, which comes from the Latin for mist, also known as a stellar nursery.
Barnard 33 is an example of a dark one. The Wings of the Butterfly one and the Red Square one are examples of the bipolar type.
nebula