Editing Bellatrix (section)

==Physical properties==
[[File:1e9m comparison Gamma Orionis, Algol B, the Sun, and smaller - antialiased no transparency.png|thumb|left|From left to right, the stars Bellatrix, the Sun, and [[Algol|Algol B]]]]
The spectral types for O and early B stars were defined more rigorously in 1971 and Bellatrix was used as a standard for the B2 III type.<ref name=walborn/> The expected brightness of Bellatrix from this spectral type is about one magnitude brighter than calculated from its apparent magnitude and Hipparcos distance.<ref name=schroder/> Analysis of the observed characteristics of the star indicate that it should be a B2 [[main sequence]] star, not the giant that it appears from its spectral type.<ref name=levenhagen/> Close analysis of high resolution spectra suggest that it is a spectroscopic binary composed of two similar stars less luminous than a B2 giant.<ref name=nieva/> 

Bellatrix is a massive star with about 8.6 times the mass<ref name=tetzlaff/> and 6.4 times the radius of the Sun.<ref name=Cazorla2017/> As a massive star, this star will [[stellar evolution|evolve faster]] than the Sun, currently it has an estimated age of approximately 25 million years.<ref name=tetzlaff/> The [[hydrogen]] should be exhausted in seven million years, after that Bellatrix will expand and cool. It may end its life in a [[supernova]].<ref name="kaler" /> The [[effective temperature]] of the outer envelope of this star is {{val|22000|u=K|fmt=commas}},<ref name=aaa515_A74/> which is considerably hotter than the 5,772&nbsp;K on the Sun. This high temperature gives this star the blue-white hue that occurs with [[B-type star]]s.<ref name=csiro/> It shows a [[projected rotational velocity]] of around 52&nbsp;km/s.<ref name=Simon-Diaz_Herrero_2014/>