IRC+10216 is a red giant star. It is a few times the sun’s mass but hundreds of times its size.
The cloud of water vapor around the star, discovered in 2001, baffled scientists because IRC+10216 is known to be a carbon star, which doesn’t make much water. They thought that the water came from the star evaporating comets or dwarf planets.
But with Herschel, the water vapor has been found to be minus 200 degrees C to 800 C, indicating that it is formed much closer to the star than the distance at which comets can exist stably. Therefore, scientists have concluded that ultraviolet light from surrounding stars reach into the dust around the star and break down the molecules there, creating oxygen. Then, the oxygen combines with hydrogen and forms water.
