Nebulae represent clouds of gas and dust which appear as hazy or fuzzy objects when viewed through a telescope and are characterized as one of four types (emission, planetary, reflection or dark). Emission nebulae, such as the Lagoon nebula (M8), simply glow, for example, with a stunning shade of red. Planetary nebulae appear as small greenish disks through a telescope, thus emulating the planets Uranus and Neptune, as a result of gas masses being thrown off by dying stars (ex. M27, Dumbbell nebula) or represent supernova remnants (ex. M1, Crab nebula). In contrast, reflection nebulae are characterized with gas surrounding young stars which reflect the stellar light (ex. M45, Pleiades) and, thus, yield beautiful images of nebulosity. Finally, dark nebulae are detectable and studied only using parts other than the visible spectrum and are believed to be associated with the formation of stars (ex. M16 in Serpens).

Note: NGC 1977 is one of the most-recognized highlights in the constellation of Orion. Although classified as an open cluster embedded within nebulosity, this area just north of the Orion Nebula is generally recognized as the Running Man Nebula owing to the emission nebulosity at the center which is in the formation of a running man. The cluster is approximately 1,500 light-years away and spans approximately 20' in diameter. It is dominated by a number of bright stars ranging from mag 4 to mag 6 and whose light reflects off gas in the immediate vicinity and thus leading to reflection nebulosity. At the same time, ionization of hydrogen gas leads to areas of emission nebulosity and as indicated by the red regions in the image below. Two other reflection nebulae sitting on the shoulders of the humanoid figure have classifications within the NGC catalog, namely NGC 1975 to the east and NGC 1973 to the west. Also, an area of protostar formation to the south is known as Herbig-Haro 45.