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'''Supergiants''' are a class of star that are among the most massive and luminous [[star|stars]] found.  The Yerkes spectral classification place supergiants with the luminosity classes of 1a (luminous supergiants), lab (intermediate luminous supergiants), or 1b (less luminous supergiants).  The largest and most luminous supergiants are termed hypergiants with a luminosity class of 0, although the term is loosely defined.  Supergiants also vary greatly in their radius, ranging from 30 times the diameter of the [[sun]] to over 1000 times.  

'''Supergiants''' are a class of star that are among the most massive and luminous [[star|stars]] found.  The Yerkes spectral classification place supergiants with the luminosity classes of '''1a''' (luminous supergiants), '''lab''' (intermediate luminous supergiants), or '''1b''' (less luminous supergiants).  The largest and most luminous supergiants are termed '''hypergiants''' with a luminosity class of 0, although the term is loosely defined.  Supergiants also vary greatly in their radius, ranging from 30 times the diameter of the [[sun]] to over 1000 times.  

Supergiants form initially the same way other regular stars do, from a cloud of [[hydrogen]] gas and interstellar dust that compresses under its gravitational attraction until the center of the cloud is hot enough to fuse hydrogen at its core.  What determines if a star will become a supergiant is the amount of mass the star contains.  A star needs to contain at least ten solar masses in order to evolve into a supergiant.<ref>http://encarta.msn.com/encyclopedia_761587630/Supergiant_%28star%29.html</ref>   

Supergiants form initially the same way other regular stars do, from a cloud of [[hydrogen]] gas and interstellar dust that compresses under its gravitational attraction until the center of the cloud is hot enough to fuse hydrogen at its core.  What determines if a star will become a supergiant is the amount of mass the star contains.  A star needs to contain at least ten solar masses in order to evolve into a supergiant.<ref>http://encarta.msn.com/encyclopedia_761587630/Supergiant_%28star%29.html</ref>