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: One of the most impressive regions of the summer sky is the large area just south of the bright star Deneb (α-Cyg, mag 1.33) and where one will find two massive emission nebulae, namely the North American Nebula (NGC 7000) and the Pelican Nebula (IC 5067 and IC 5070), separated by a thin dark dust lane. The Pelican Nebula lies at a distance of 1,900 light-years away and spans 15 light-years in diameter. It is often depicted in two forms; the larger widefield version encompasses the complete nebula and is designated as IC 5070 whereas a smaller region with protruding tendrils and near the neck of the "pelican" is also often referred to by the same name but under a different designation within the IC catalog (IC 5067). The rich emission is associated with star formation and it is expected that this area of the sky will look dramatically different in a few million years owing to a plethora of new stars and a significantly reduced amount of hydrogen.

Note: For an LRGB version of IC 5067 (Pelican nebula) from 2008, click here.