The Coalsack is probably the best-known nebula in our Milky Way that can be seen with the naked eye in the southern starry sky. It neighbors directly on the constellation “Southern Cross”, which stands out from the millions of other stars with its three blue and one yellow star. The coal sack belongs to the group of dark clouds. Dark clouds are large clouds of interstellar matter, mainly dust, which absorb the light of the stars behind them and thus darken them. This is the only way dark clouds are visible to us.
Coalsack and Southern Cross