Coalsack Nebula

The Coalsack Nebula (Southern Coalsack, or simply the Coalsack)[3] is a dark nebula, which is visible to the naked eye as a dark patch obscuring part of the Milky Way east of Acrux (Alpha Crucis) in the constellation of Crux.[2]

Coalsack Nebula
Dark nebula
The Coalsack Nebula taken by the Wide Field Imager on the MPG/ESO 2.2-metre telescope[1]
Observation data: J2000.0 epoch
Right ascension12h 50m
Declination−62° 30′
Distance180[2] pc
Apparent magnitude (V)–
Apparent dimensions (V)7° × 5°
ConstellationCrux
Physical characteristics
Radius30–35 ly
Absolute magnitude (V)–
Notable features–
DesignationsCaldwell 99

General information

Historically any other dark cloud in the night sky was called coalsack. The Coalsack Nebula was juxtaposed in 1899 by Richard Hinckley Allen through naming the Northern Coalsack Nebula.[4]

The Coalsack Nebula covers nearly 7° by 5° and extends into the neighboring constellations Centaurus and Musca.[5] The first observation was reported by Vicente Yáñez Pinzón in 1499.[6] 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.[6]

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.

In Australian Aboriginal astronomy, the Coalsack 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 do not 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.[7] There is also a reference by Gaiarbau (1880) regarding the coalsacks replicating bora rings on Earth. These astronomical sites allowed the spirits to continue ceremony similar to their human counterparts on Earth. As bora grounds are generally located on the compass points north–south, the southern coal sack indicates the ceremonial ring.

In Inca astronomy this nebula was called Yutu, after a partridge-like South American bird,[8] or Tinamou.[9]

References
  1. "A Cosmic Sackful of Black Coal". Retrieved 15 October 2015.
  2. Franco, G.P.A. (2000). "Interstellar Na I D lines towards the Southern Coalsack". Monthly Notices of the Royal Astronomical Society. 315 (3): 611–621. Bibcode:2000MNRAS.315..611F. doi:10.1046/j.1365-8711.2000.03434.x.
  3. "Coalsack Nebula". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2018-09-30.
  4. O'Meara, Stephen James (2012-04-23). "Where is the Northern Coalsack?". Astronomy.com. Retrieved 2023-02-10.
  5. Darling, David J. (2004). The universal book of astronomy: from the Andromeda Galaxy to the zone of avoidance. Hoboken, New Jersey: Wiley. p. 351. ISBN 0471265691.
  6. "The Coalsack and the Southern Cross". ESO. 3 December 2009. Retrieved 1 October 2018.
  7. Songs of the Songmen, 28–30.
  8. James B. Kaler (2002). The Hundred Greatest Stars. New York: Springer Science & Business Media. p. 5. ISBN 978-0-387-95436-3.
  9. A. F. Aveni, ed. (2010). Archaeoastronomy in the New World : American primitive astronomy : proceedings of an international conference held at Oxford University, September, 1981. Cambridge: Cambridge University Press. ISBN 978-0521125475.
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