Coalsack Nebula
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| Coalsack Nebula | |
 The Coalsack Nebula |
|
| Observation data (Epoch J2000.0) | |
|---|---|
| Type | Dark |
| Right ascension | 12h 50m |
| Declination | −62° 30′ |
| Distance | 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 | – |
| 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 Vincente Yanez Pinzon in 1499. The Coalsack is located at a distance of approximately 600 light years away from Earth, in the Crux constellation.
[edit] General information
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[citation needed], its first observation was reported by Vincente Yanez Pinzon in 1499. It was named “il Canopo fosco” by Amerigo Vespucci and was also called “Macula Magellani” (Magellan's Spot) or “Black Magellanic Cloud” in opposition to the Magellanic Clouds.
In 1970, K. 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 does not have an identification number. It is prominently featured in the Larry Niven and Jerry Pournelle science fiction novel The Mote in God's Eye.
![A depiction of the "[Emu] in the sky", which is an Australian Aboriginal constellation consisting of dark clouds rather than of stars. The European constellation on the right is crux or the Southern Cross, and on the left is Scorpius. The head of the emu is the Coalsack.](../../../../images/local/f/fb/Emu_public.jpg)
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.
