Like a rainbow, its daylight equivalent, a moonbow is produced when light is broken up into its constituent colours as it passes through water droplets.
月虹与白天出现的彩虹一样，是光通过水滴分解成多种色光后产生的，而光本身是由多种色光组成的。
2
He saw that the constituent parts were being separated, with hydrogen gas falling into the star while water vapour remained farther out and the dust was farther out still.
他发现组成部分正在分离——氢气落入恒星里面，而水蒸汽留在外围，尘埃还在更外面。
3
Water vapor is a normal constituent of the atmosphere.