The European Southern Observatory has published a new Very Large Telescope photo of the cometary globule CG4 or, like they call it, The Mouth of the Beast. As the ESO says, as with other cometary globules, "the exact nature of CG4 remains a mystery".
There are two theories. Some astronomers think that CG4 may have started as a spherical nebulae, the product of a supernova, and then their shape could have shredded by other nearby supernova explosions. Other astronomers believe that they are "shaped by stellar winds and ionising radiation from OB stars — a type of massive stars that produces a lot of ultraviolet radiation.
There are many examples of these cometary globules. This one is located 1300 light-years away from Earth, in the constellation of Puppis.