M16: Dust and an Open Cluster . ... Credit Copyright: Anglo-Australian Telescope Board Explanation: The photogenic M16 shown above is composed of a young star cluster and a spectacular emission nebulae lined with distinct regions of interstellar dust . ... The redness of the surrounding emission nebula gas is caused by electrons recombining with hydrogen nuclei, while the dark regions are dust lanes that absorb much of the radiation that enters it. ... NASA Official: Jay Norris. ...