Gas cloud
In astronomy , gas clouds are extensive areas that are filled with light gases and usually some dust . In visible light, they are often demarcated by dark clouds embedded in or in front of them . If new stars are formed in them during compression processes, they are also called star formation regions.
When stars are formed in large gas clouds, an open star cluster is usually formed . The total stellar masses only make up about 10% of the cloud mass. Then the radiation pressure from these new stars causes the rest of the gas to be dispersed.