| Coalsack Nebula | |
|---|---|
The Coalsack Nebula |
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| Observation data (Epoch J2000.0) | |
| Type | Dark |
| Right ascension | 12h 50m |
| Declination | −62° 30′ |
| Distance (ly) | 600 ly |
| Apparent magnitude (V) | – |
| Apparent dimensions (V) | 7 × 5 ° |
| Constellation | Crux |
| Physical characteristics | |
| Radius | 30–35 ly |
| Absolute magnitude (V) | – |
| Notable features | – |
| Other designations | C99 |
| See also: Dark nebula, Lists of nebulae | |
The Coalsack Dark Nebula (or simply the Coalsack) is the most prominent dark nebula in the skies, easily visible to the naked eye as a dark patch silhouetted against the southern Milky Way. It was known pre-historically in the Southern Hemisphere and was observed by Vicente Yáñez Pinzón in 1499. The Coalsack is located at a distance of approximately 600 light years away from Earth, in the Crux constellation.
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The Coalsack Dark Nebula covers nearly 7° by 5° and overlaps somewhat into the neighbour constellations Centaurus and Musca. Although this nebula was known to the people of the Southern Hemisphere in prehistoric times,[1] its first observation was reported by Vicente Yáñez Pinzón in 1499. It was named “il Canopo fosco” (the dark Canopus) by Amerigo Vespucci and was also called “Macula Magellani” (Magellan's Spot) or “Black Magellanic Cloud” in opposition to the Magellanic Clouds.
In 1970, Kalevi Mattila proved the Coalsack is not totally black; it has a very dim glow (10% of the brightness of the surrounding Milky Way) which comes from the reflection of the stars it obscures.
The Coalsack is not present in the New General Catalogue and in fact does not have an identification number (outside of the Caldwell Catalogue, in which it is C99).
The Coalsack is important in Australian Aboriginal astronomy, and forms the head of the Emu in the sky in several Aboriginal cultures. Amongst the Wardaman people, it is said to be the head and shoulders of a law-man watching the people to ensure they don't break traditional law. According to a legend reported by W.E. Harney, this being is called Utdjungon and only adherence to the tribal law by surviving tribe members could prevent him from destroying the world with a fiery star.[2]
In Inca astronomy, this nebula was called Yutu, meaning a partridge-like southern bird.[3]
The Coalsack is mentioned in the Star Trek: The Original Series episodes "The Immunity Syndrome" and "Let That Be Your Last Battlefield", as well as "2001: A Space Odyssey" by Arthur C. Clarke.
The Coalsack figures prominently in the Larry Niven and Jerry Pournelle's science fiction novel The Mote in God's Eye and its sequels, The Gripping Hand and Outies[4].
Coordinates: 12h 52m 19s, −62° 25′ 28″
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