OB star

250px|thumb|LH 72 is one of the OB associations present in the Large Magellanic Cloud.

OB stars are hot, massive blue stars. They are stars of types O or B in the HertzsprungRussell diagram. 

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 

Other websites
 Scientia Astrophysical Organization's star classification page.  
 Philippe Stee's homepage: Hot and active stars research

Category:Types of stars