ESA’s Herschel Infrared Space Observatory has discovered the role of ultraviolet light in the creation of water in space. Water is a rare commodity in space and on Earth is an essential ingredient for life, along with carbon compounds.

Astronomers have seen gigantic clouds of water vapor surrounding dying carbon stars that shouldn’t produce much water. Astronomers thought the star’s heat may be evaporating comets or dwarf planets to produce the water, but the vapor was too close to the star for a comet or other icy body to exist. The temperatures were too high too. The water vapor temperatures range from -200º C to 800º C, which was also too hot for icy celestial bodies to exist.

Herschel revealed the water vapor cloud by looking through a huge dust envelope around the star. The dust absorbs visible radiation and emits infrared light. The ultraviolet light from other stars penetrates the dust cloud envelope and breaks up molecules in the dust, like carbon monoxide and silicon monoxide, freeing oxygen atoms. Hydrogen atoms then attach to the oxygen atoms, forming water. Water is one oxygen atom and 2 hydrogen atoms.