Fr.: globule cométaire
A relatively small cloud of → dust and → gas in the → interstellar medium shaped like a comet with a bright-rimmed head. Cometary globules are situated near young → massive stars with a strong → stellar wind. The wind ionizes gases on the side facing the → O stars and sweep away the low-density gas toward the tail. Cometary globules are believed to be → molecular cloud condensations, which are so dense that they are not disrupted when an → H II region expands into the molecular cloud surrounding it. The → Rosette nebula is a good example of an H II region which shows an abundance of cometary globules.