radiation-bounded nebula An emission nebula whose central star or stars is not hot enough to ionize the entire cloud of gas. The visible extent of the nebula is thus limited by how much ionizing radiation is available, not by the overall size of the cloud or by the amount of material it contains. Compare with a gas-bounded nebula. Related category • NEBULAE AND STAR CLUSTERS Also on this site: Encyclopedia of Alternative Energy & Sustainable Living Encyclopedia of History Transport Concepts & Designs (partner site) |