Yıldız sınıflandırma (astronomi): Revizyonlar arasındaki fark

▲Class '''B''' stars are extremely luminous and blue. Their spectra have neutral helium, which are most prominent at the B2 subclass, and moderate hydrogen lines. Ionized metal lines include [[magnesium|Mg]] II and [[silicon|Si]] II. As [[OB star|O and B stars]] are so powerful, they only live for a very short time, and thus they do not stray far from the area in which they were formed. These stars tend to cluster together in what are called [[OB association]]s, which are associated with giant [[molecular cloud]]s. The Orion OB1 association occupies a large portion of a [[spiral arm]] of our [[Milky Way|galaxy]] and contains many of the brighter stars of the [[Orion constellation|constellation Orion]]. About 1 in 800 of the main sequence stars in the solar neighborhood are Class '''B''' stars.<ref group="nb" name="proportions" /><ref name="LeDrew2001" />.