Like the gaping mouth of a gigantic celestial creature, the cometary globule CG4 glows menacingly in this image from ESO’s Very Large Telescope. Although it looks huge and bright in this image it is actually a faint nebula and not easy to observe. The exact nature of CG4 remains a mystery.
Image Credit: ESO
Explanation from: http://www.eso.org/public/images/eso1503a/