Vast clouds of hydrogen mixed with tiny dust grains are distributed throughout the Milky Way. The hydrogen only becomes visible when it is illuminated by ultraviolet light very hot stars, which causes the gas to glow (fluoresce) with a characteristic red colour. In most cases, such as here, the hot stars formed recently from the hydrogen cloud, and are thus intimately associated with it.

The light from the stars found at the heart of the Trifid Nebula are here seen associated with dust lanes which are silhouetted against the glowing background. This intricate nebula is in the constellation of Sagittarius at a distance of about 3000 light years.

Image derived from an AAT plate taken in red light