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Coalsack

or Coal Sack

[kohl-sak]
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noun Astronomy.
  1. a dark nebula in the southern constellation Crux, whose dust particles obscure light from Milky Way stars behind it.

Origin of Coalsack

First recorded in 1625–35; coal + sack1
Also called Southern Coalsack.
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018