Unformatted text preview: by a supernova explosion, or by other mechanisms • O and B Stars and Their Relation to H II Regions • The most massive protostars to form out of a dark nebula rapidly become main sequence O and B stars • They emit strong ultraviolet radiation that ionizes hydrogen in the surrounding cloud, thus creating the reddish emission nebulae called H II regions • Ultraviolet radiation and stellar winds from the O and B stars at the core of an H II region create shock waves that move outward through the gas cloud, compressing the gas and triggering the formation of more protostars. • Supernovae compress the interstellar medium and can trigger star birth...
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- Fall '10
- Astronomy, Interstellar medium, Giant molecular clouds, giant molecular cloud, Young star clusters