Dark Horse (astronomy)
Dark Horse Nebula
|Observation data: J2000.0 epoch|
|Right ascension||17h 21m|
|Apparent magnitude (V)||–|
|Apparent dimensions (V)||??|
|Absolute magnitude (V)||–|
|Designations||Great Dark Horse|
|See also: Lists of nebulae|
The Dark Horse Nebula or Great Dark Horse is a large dark nebula, which as seen from Earth, obscures part of the upper central bulge of the Milky Way. The Dark Horse lies in the equatorial constellation Ophiuchus (the Serpent Bearer), near its borders with the more famous constellations Scorpius and Sagittarius. It is a significant, visible feature of the Milky Way's Great Rift.
This region of dark nebulae is called Dark Horse because it resembles the side silhouette of a horse and appears dark as compared with the background glow of stars and star clouds. It is also known as "Great" because it is one of the largest (in apparent size) groups of dark nebulae in the sky.
The rear of The Great Dark Horse (its rump and hind legs), is also known as the Pipe Nebula, which itself carries the designation B77, B78, and B59. (The 'B' numbers named after the astronomer Edward Emerson Barnard, who catalogued dark nebulae.) The Snake Nebula extends from the Dark Horse to the Rho Ophiuchus nebulosity.
The ability to see The Great Dark Horse with the naked eyes is an indication that the skies are very dark, i.e. not affected by (urban and industrial) light pollution.
- The Pipe Dark Nebula, basic information on dark nebulae in the region.