Like other giant stars they are short lived, and do not move far from where they were formed. During their lifetime, they emit huge amounts of ultraviolet radiation. This radiation ionizes the surrounding interstellar gas of the nebula, forming an H II region.
References[change | change source]
- B. Cameron Reed (2003). "Catalog of galactic OB stars". The Astronomical Journal. 125 (5): 2531–2533. Bibcode:2003AJ....125.2531R. doi:10.1086/374771.
Other websites[change | change source]
- Scientia Astrophysical Organization's star classification page. 
- Philippe Stee's homepage: Hot and active stars research