Messier's catalog does not contain any dark nebula.
The icon shows the Horsehead Nebula
Besides the luminous bright nebulae of various types, consisting of light
emitting gas or illuminated dust masses, there are dark nebulae which can be seen
because they obscure the light coming from stars or bright nebulae behind them.
A famous example is the Horsehead Nebula.
Last Modification: 25 Jan 1998, 16:00 MET