The Horsehead Nebula, found in the constellation Orion
is probably one of the most identifiable nebulae
in the sky.
It is part of a dark molecular
cloud, and is shaped like - you guessed
it - a horsehead. It is visible as it is in front of a larger red diffuse nebula (IC 434) which consists mostly of hydrogen
It is located near Alnitak (or Zeta Orionis), which is the easternmost star in Orion's Belt, and whose radiation causes the background nebula
It is approximately 1,500 light years away.