The Sharpless catalog of emission nebulae contains 313 entries representing H-II emission nebulae with a declination of -27 degrees or above.
Compiled and published by American astronomer Stewart Sharpless (USNO) in 1959 (see
here), the catalog contains a wide variety of
star formation regions across the Milky Way including various Herbig-Haro and Wolf-Rayet objects as well as a number of well-known emission
nebulae such as the Trifid (M20), the Eagle (M16), Orion (M42), Lagoon (M8), the Crescent
(NGC 6888), and the Crab (M1) nebula.
Note: The large and dim emission nebula Sh2-155 in Cepheus lies at a distance of 2400 light-years away and spans
another 35 light-years across. It is characterized with rich H-II emission nebulosity with the northern half of the nebula being significantly
brighter than the southern half. Commonly referred to as the Cave Nebula owing to a circular formation near the center resembling a cave,
Sh2-155 is also characterized with reflection nebulosity (vdB 155) and as indicated by the small bluish nebulosity to the lower right as well
as dark nebulae to the southwest. Star formation in Sh2-155 is believed to be low.
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