Monday, April 11, 2011

The Coal Sack and the "Emu in the..." er, I mean... the "Llama in the Sky"?!

By Duane Hamacher

On a clear winter night in the Southern Hemisphere, the bright stars of the Southern Cross shine above, flanked by the Pointers (Alpha and Beta Centauri) to the left and the False Cross to the right (Figure 1).  Just below the Southern Cross (called Crux), to the left, you can clearly see a dark patch, called the Coal Sack by astronomers.  The Coal Sack is an absorption nebula (an expanse of cool gas and dust that absorbs background light, making it appear dark) approximately 600 light years away and 20-30 light years across.  Other absorption (aka Dark) nebulae include the Horsehead, Cone, and Snake Nebulae.


Figure 1: The Pointers, Coal Sack, and Southern Cross.
Image by Duane Hamacher, using the Starry Night software package.

Aboriginal Australians have diverse views of the Coal Sack (Figure 2).  Given the dark, cave-like appearance of this nebula, some Aboriginal groups identify it as the lair of evil beings.  For example, in the oral traditions of the Yolngu, Ngarinman, and Wardaman peoples of the Northern Territory, an evil spirit-being lurks in the Coal Sack and flings a fireball (an exceptionally bright meteor) from the heavens to destroy the world if sacred laws are broken or traditions are ignored.   Similar views are held by the  Puckowe of the Lower Murray River region, Gundidjmara people in southwestern Victoria, Wiradjuri of central New South Wales, and the Wardaman of the Northern Territory.


The Tangani people of the Coorong saw a meteor come from the Coal Sack, which they called Yuuki, that coincided with a smallpox epidemic in the 1800s.  The meteor, which was “like a bright flash, too bright to look”, was believed to be a spirit-man named Kuldalai who traveled across the sea towards Kangaroo Island.  Descriptions of meteors emanating from the Coal Sack may be related to the Alpha and Beta Centaurids, meteor showers that radiate from near the Pointers and very close to the Coal Sack.  In fact, just yesterday, near the town of Armidale, New South Wales, I witnessed a meteor near the Coal Sack - what a beautiful sight!


 Figure 2:  A close-up image of the Coal Sack, with Acrux and Becrux to the upper right.
Image by Gail Bischoff.

Similarly, some South Australian groups describe the Coal Sack as a large waterhole in the Sky River (Milky Way), which is the home to a serpent or bunyip (monster).  In Central Australia, the Arrernte refer to it as the nest of the wedge-tailed eagle, Waluwara.  However, the Coal Sack is most frequently linked with an emu.  While many groups refer to the nebula simply as “the emu”, others describe the full figure of the animal.  Instead of being traced out by the bright stars, the body is traced out by the dark dust lanes of the Milky Way.  If you look carefully at the Coal Sack, you can see the shape of the emu’s head: the dust lane that forms the shape of a beak, the overall “roundness” of the head, and the star BZ Crucis, a 5.3 magnitude blue sub-giant star ~1,000 light years from earth, in a serendipitous position to look like the emu’s eye (see Figure 2).  The body of the emu is traced out by the dust lanes of the Milky Way to the east of the Pointers, into the galactic bulge (Figure 3).




Figure 3: Top - An emu.  Image by Australian Animals.
Bottom - The Emu in the Sky.  Image by Alec Kennedy.

In Victoria, Wergaia clans called the emu Tchingal, while the Mara called it Torong.  The “emu in the sky” is known across Australia, from the Kamilaroi of New South Wales, to the Meintangk of South Australia, to the Larrakia of the Northern Territory.  The famous emu rock engraving at Elvina Track in Kuringai Chase National Park north of Sydney may have a connection to the night sky.  The engraving is one of many examples of rock art in the park, which include rock engravings, paintings, stone arrangements, and axe grinding grooves, among others.  A look at the emu engraving will bring to your attention something unusual - her feet are pointed behind her, as if she were flying (which, of course, emus can’t do).  It was proposed by Professor Hugh Cairns of Sydney University that this may represent the “Emu in the Sky”.  Later, Professor Ray Norris of the CSIRO and his son, Barnaby, photographed both the engraving and the night sky, oriented appropriately.  What they found was remarkable… the emu aligns to her image in the night sky at the time of year that emu eggs are ready to be collected (late May and early June, Figure 4).  Emu eggs were an important food source for Aboriginal people, and the engraving features an egg within the emu herself.  The image won Barnaby Norris a Eureka prize and has become the definitive symbol for Aboriginal Astronomy today.


Figure 4: The "Emu in the Sky" engraving, as seen from Elvina Track, Kuringai Chase National Park, north of Sydney.  Image by Barnaby Norris.

Interestingly enough, this pattern is known all the way across the Pacific but is instead related to another animal.  In the Andes of South America, the outline of the Australian “emu in the sky” is instead referred to as a “llama in the sky” (Figure 5).  The Inca revered the llama, which can be seen as a very similar shape to the emu in the sky, except that the Pointers are the llama’s eyes.  For this reason, llamas with black fur are especially important in Inca religion.  In Inca legend, the llama (Yacana) was traveling with her baby across the sky river (Milky Way). The further she walked, the blacker her fur became.  When the baby was hungry, Yacana fed it.  When she awoke, it became daylight.  To this day, when a man walks near the place Yacana fed her baby, he will be blessed with good luck.


Figure 5: The "Llama in the Sky", found in Inca legends.  Image by Brian Ritchie.

In Bolivia, this asterism is seen as a rhea (a bird very much like an emu or ostrich)!  So next time you are looking up at the night sky, take a minute to look for the emu in the sky... you'll never see it the same again!

Further Reading:
The Legend of Yacana, by Antonio Claret
The Astronomy of Aboriginal Australia, by Ray Norris and Duane Hamacher

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We respectfully acknowledge all Aboriginal groups mentioned in this article.


1 comment:

  1. Australian Aboriginal astronomy is a name given to indigenous Australian culture relating to astronomical subjects such as the Sun and Moon, the stars, planets, and the Milky Way, and their motions on the sky.

    Because the Australian Aboriginal culture is the oldest continuous culture in the world, it is possible that the Australian Aboriginal people may be the world's first astronomers.


    Thanks for sharing!!!!!!

    ReplyDelete