Dark nebulae B72 and B68. True-colour optical image of the dark nebula B72 (also known as the Snake, or Barnard's S-nebula, upper left) and B68 (dark patches below B72) in the constellation Ophiuchus. These nebulae have no light of their own, being composed of dense dust and gas, and are only visible because they block the light of the rich starfields behind them. It is thought that these clouds may, in time, condense into star- forming regions. The bright star at bottom centre is Theta Ophiuchi, with Omicron and 44 Ophiuchi at far right and left respectively. This image was produced by digitally combining photographs taken by the UK Schmidt Telescope in blue and red light.