The Eagle Nebula (NOT a planetary nebula) is an immense structure of columns or pillars of gas and dust
located some 7000 lightyears away toward the constellation Serpens.
If you turn your head 90 degrees counterclockwise, you will see an eagle from the side, having just caught a fish (or a boot).
The Eagle Nebula is a site of new star formation. The pillars, several lightyears long, are concentrations
of dense molecular gas, which are able to withstand the effects of the intense
ultraviolet light emitted by newly-formed hot, massive stars, located
above the nebula.
The knots and filaments on the surfaces of the pillars are formed as
the surface of the pillars - heated by the hot stars - boils away. In this image,
red shows light from singly-ionized Sulphur, green shows light from neutral
Hydrogen, and blue shows light from doubly-ionized Oxygen.
The red spot in the eagle's butt is due to gas being heated and ionized from a jet coming from a protostar in the bottom of the image. This protostar is itself hidden in the dust, but is visible in infrared images.