Type O star
A star of the spectral class O; a bright blue-white star. They are massive and very luminous, indicating extremely high temperatures (~20,000 K and up). The O type stars are the first and brightest in the sequence of spectral types, and are distinguished by lines of ionized helium, nitrogen and oxygen. Often neutral helium and weak hydrogen lines are also visible. Type O stars strongly modify the medium in which they were born.
Being so hot and bright this type of star burns up all its fuel very quickly. When it collapses, having exhausted all its fuel, an O type star will usually become a large black hole. An O5 will spend only about million years on the main sequence. These stars therefore are very rare, on average about one in every billion cubic light years of space. Only one star in 4 million is an O type. Despite having an expansive life-zone, O type stars never have life-supporting planets, as they do not endure long enough for life to form.
Good examples are Zeta Puppis (Naos) and Iota Orionis A.
